My strategies for avoiding sex had run out and so, as the inevitable happened, I simply hoped my boyfriend could not tell that I was enduring, rather than enjoying, our encounter.
John was a virgin when we met, so I assume he did not realise how strange and dysfunctional our perfunctory couplings were.
We'd abstain for months until, finally, he'd start bribing me with gifts to go to bed with him. But I loathed it. I dreaded the foreplay, and the act itself repulsed me. I could only bear it by focusing my mind on something else.
It's not that John was a particularly inept lover - he wanted very much to please me - nor was this a terminal case of bedroom boredom. The problem is that I have always detested sex: the idea of it, the fact of it, and the repellent notion that society seems to revolve around it.
I am 29 and I have had three lovers, two of whom I lived with. I have tried to quell the disgust I feel at the prospect of sex, but have failed repeatedly to do so.
There is nothing physically wrong with me - doctors have confirmed this - and I am not afflicted by guilt. My parents had a healthy and open attitude to sex. There is no dark incident lurking in my past that would explain my abhorrence: I have not been abused nor mistreated, and I have never been coerced into having sex against my will.
I am not gay, and I feel no physical attraction towards women. I do not think anything is 'wrong' with me, although perhaps my attitude would have been considered less freakish if I had been born in the Victorian era.
I just hate sex, and have decided I will never put myself through the torture of it again. I am in my physical prime, but my sex life is over. I wish it were not so. My tragedy is that I want to be 'normal'. I crave the companionship of a man. I would love to be married; to build a home, to enjoy the comfort and domesticity of a life-long relationship with a partner I could cherish. I want to love and be loved.
I do not find men themselves abhorrent. On the contrary, I appreciate their looks and enjoy their company. I like cuddles, I don't mind kissing and I yearn for affection; but nothing more than that.
I have researched internet sites and discovered that only one per cent of the population is, like me, asexual. Of these, half are men and a smaller proportion is gay.
So I have resigned myself to the fact that there is scant chance of my finding a man I love who, like me, wants a celibate relationship.
I have not discussed my lack of libido with my parents - in a sense, this article is my 'coming out' - but I know it saddens them that the wedding and grandchildren they yearn for have not been forthcoming.
Perhaps they believe I just haven't met the right man yet. I can assure them, however, that I have persevered with sex for long enough to know that for me it is a misery and a penance.
Why should I endure it, just to make other people happy?
I have known since my teenage years that I am different from my peers. I grew up in Buckinghamshire, where I still live with my parents, and attended a girls' grammar school.
While my friends were devouring teen fiction and sniggering over the salacious nuances in it, I was immersed in animal stories. I found sex-education lessons alien and embarrassing: I did not see how they could ever apply to me.
When my friends started pairing off with boys, I could not identify with them. While they bought make-up and made covert visits to Ann Summers shops, I enjoyed ballet and my beloved pets.
One by one they lost their virginity, and described the fact to me in dreadful detail. I couldn't see how any of it applied to me, but reassured myself that once I had a boyfriend, everything would fall into place.
It didn't. My best friend, Stephanie, introduced me to Adrian, her boyfriend's pal, in the summer of 1999, when I was 16. Adrian was 19 - sweet, funny and slightly overweight. I liked him: we shared the same interest in trashy TV, and he didn't seem to mind that I was a bit of a nerd.
I decided I was going to lose my virginity to him as quickly as possible, to silence my friends - who considered me abnormally prudish - and to be like everyone else.
So, three months after we started going out, I slept with Adrian for the first time on his rumpled bed at his parents' house, one afternoon when they were both at work.
There was no romance, but I didn't want that. I wanted to get it over and done with, as you would some tedious chore. Adrian, who'd had two previous relationships, knew it was my first time. He was kind and patient, but he hadn't bargained for the level of fear and panic I felt.
Afterwards, I felt only revulsion, but I was determined to persevere.
I stayed with Adrian at weekends, making sure sex was the first thing on the agenda when I arrived, so we could get it over with and progress to things that were interesting and fun.
But each encounter confirmed that I was repelled by it. I learned to fake pleasure but afterwards, while Adrian slept, I stared at the ceiling and silently cried.
Eventually, realising the true nature of my feelings, he was angry and hurt. We'd been together for nine months; I was due to take up a place to read anthropology at the University of Surrey, in October 2000 and it seemed the right moment to separate, so we did.
But I felt distraught; convinced there must be something physically wrong with me that was preventing me from enjoying sex.
The doctor gave me a check-up and did several tests, all of which confirmed my hormone levels were normal and that there was nothing physically untoward. Still, though, I continued to feel like a freak, an outsider.
NOT TONIGHT, DARLING
Some 62 per cent of men said they turn down sex more frequently than their female partner, according to research.
At university, I was lonely and miserable. It seemed everyone else was having lots of fantastic sex, when all I wanted was a cuddle and a companion.
After five months there, I could stand it no longer. In February 2001, I moved back home to my parents.
My friends from school had all paired up and gone off to pursue their dreams, and my sense of isolation deepened.
When I met John, my next boyfriend, three years later, I think I just felt grateful that anyone wanted me. He was a friend of a friend. I was 20; he was 23, worked in retail management and had never had a girlfriend.
We were two lonely people, and he was almost absurdly grateful that I was taking an interest in him.
So we started seeing each other - and I steeled myself for the inevitable. After a month or so, when I felt I could procrastinate no longer, we slept together. It was every bit as awful as I had feared.
However, a shared dread of loneliness and a need to conform propelled us into a relationship. We rented a two-bedroom terrace together, acquired two cats, and for much of the time life was fine.
I started work in the same DIY store as John - I'm still there now - and in my spare time wrote teen fiction and poetry, which remains my real passion.
In the evenings we ate together, then curled up on the sofa watching films on television. My parents hoped for a wedding and grandchildren, but I knew that neither would happen.
The problem, of course, was sex. The idea of it remained abhorrent to me, and I found 1,000 reasons to avoid it.
Although John and I only had sex once every three or four months, I found it so repellent I ceased even to fake enjoyment. Poor John would have done anything to please me, but I could never tell him that the only way to make me happy was for us both to take a lifetime's vow of abstinence.
Remarkably, we stayed together for seven years but, inevitably perhaps, John finally left me for another woman. I just felt relieved that it had ended, and that the charade was over.
At 27, I went back to live with my parents, feeling disillusioned and convinced of my weirdness.
I sought help from a psychosexual therapist. She said: 'If you hate sex and you're fine with that, you have no problem. If you don't want to hate it, you do have a problem.'
I had a problem. So I visited the therapist for six weeks, but talking about sex made me squirm with discomfort and eventually I realised it was pointless to continue. I stopped going to the sessions.
I had assumed there was something about me that needed to be fixed. It didn't occur to me that I could just accept the way I was.
And then, in July 2011, I met Owen in a local bar. He was tall, slim and athletic, with curly hair and a beard: close to my idea of physical perfection in a man.
He seemed shy, which was a good fit for me, and was working as a barman while he studied for an engineering degree at London University.
Meeting him ignited a spark of optimism in me. Owen was so attractive, I even nurtured a hope that if I had sex with him, my revulsion might finally evaporate.
I dared to believe he might change me; that all I needed was to be with someone like him and then I would become a normal, functioning partner.When we started dating, I felt happy and full of hope. And when, after just two weeks, it became obvious we would have sex, I was neither fearful nor tense. Actually, I was looking forward to it.
But as things progressed, the old dread and revulsion consumed me. I felt confused and angry: why was I such a freak?
I didn't know what to do, who to talk to or where to go. I felt lost. So what did I do? I dissembled, as I had so many times before. I'd become such a proficient actress that I don't think Owen suspected my true feelings.
We moved in together two months later and I was prepared to play at happy families. Sometimes, I even initiated sex because I wanted so much for him to love me.
But it was all a sham. We broke up last April, after eight months together, just as I had begun to find excuses for not sleeping with him. There was housework to do; I had a headache.
How could I tell him the truth: that he was gorgeous, but I found intimacy repulsive?
So, once again, I am back living with my parents. Loneliness haunts me. Although I go through the motions of a normal life - I occupy myself with ballet classes, gym, Pilates and the odd outing to the pub - I know I do not fit in.
You may wonder how I can be so sure, at 29, that I will not change. My response is: would you ask a gay person the same question? I make the parallel because it used to be thought that gay people could be treated or have therapy to make them heterosexual. It didn't work any more than it would 'cure' me of my asexuality.
My friends are few, and most of them are engaged or married. I do not tell them I find sex disgusting. Why should I? They would only regard me with puzzlement and disbelief. Certainly, none of them could empathise with me.
I haven't discussed my problem with anyone. Whenever female friends have discussed sex I played along, pretending I shared their interest in it.
John knew I hated sleeping with him - we were together too long for that not to have been obvious - but it became the elephant in the room. We didn't discuss it; I think we both feared that would make the problem worse.
Seven months ago, I began to wonder if anyone else shared my problem. I stumbled on a website called Asexuality Visibility & Education Network. Actually, it was a comfort to discover there are others in the world who never want to have sex.
And by writing this article, I hope more people will be emboldened to admit they feel the same way as me.
But there aren't many of us, and I know my chances of finding an asexual partner - a man I love but who never wants to have a physical relationship - are remote.
Still, I hope that one day I may discover him and marry. I do not want children of my own. The idea of carrying a baby repulses me as much as the act of procreation itself. I feel it is unnatural.
People say that, as I get older, I may change my mind. I wish I could say there was a glimmer of hope that I would, but I have absolutely no sense of a biological clock ticking. If ever I do want children, I will adopt.
My mind is made up: I will not have sex again. This may consign me to a lonely life, but it is better than deceiving a man I love.
A relationship based on such a sham is the ultimate lie.