I admit that I used to enjoy masturbating now and again. An evanescent veneer of guilty shame always followed the climax, but once I was quite certain that no one else knew about my furtive five-finger rendez vous, it was worth it.

Now that others are waiting on me to "produce a sample", it is an entirely different activity. Now it is fraught not just with globules of guilt, but also stage fright, gross embarrassment and a crimson degree of shame. It is no longer a blend of avid sportsmanship and immature (and sometimes premature) joy kept behind closed doors. No, it has become a clinical exercise, performed out of necessity, with my wife and hospital staff fully aware of what I am doing and waiting for me to produce the goods - which are then to be subjected to possibly humiliating tests and analysis.

The reason? After doggedly trying for well over 18 months to conceive without even a nibble, my wife and I sought medical help.

Think of six couples you know. The chances are that one of those couples will experience difficulty in conceiving. In our circle of family and friends, five couples have recently given birth to their first child, or soon will. We are the odd one out. This hits home and makes the reality much tougher to bear when we meet for dinners or family gatherings.

For nearly 30% of those couples who seem unable to conceive, the reason for their problems can remain a mystery. Once all the plumbing has been through preliminary tests, without throwing up anything obvious, they can expect a diagnosis of "unexplained infertility", and then another round of testing.

Before I launch into the gritty details, however, I readily admit that assisted reproduction routines - undergoing a string of tests to diagnose why my wife and I seem unable to conceive, followed by a number of procedures to try to facilitate it - are much more demanding, humiliating and invasive on the woman in the relationship.

But that doesn't diminish the toll it takes on men, or lessen the physiological and psychological effects it can have: it can undermine your manhood, render your libido listless and leave you wallowing in denial, humiliation, guilt and shame. It is also likely to put additional stress on an already tested relationship. Not ideal conditions for making babies.

For men, the main cause of infertility is poor sperm quality. So the first thing I endured, in the company of my wife, was a series of questions about my sexual past. I was then handed a small plastic tub to fill at my leisure. Fortunately, I was given the choice of coaxing the ejaculate out either at home or in a room at the hospital. I didn't even bother to ask to see the room's hospitable amenities.

While men may be able to produce sperm into our 70s, and so aren't as attuned to, or governed by, the biological clock, sperm are a pathetic lot at the best of times: a measly 15% of an average ejaculation of 100-300 million sperm are healthy enough to fertilise an egg. Of these, only four or five dozen survive the journey.

Every sperm is, therefore, sacred, so it is critical that men do not hamper the production of healthy ones. According to Katrina Win, our supremely supportive nurse at Guy's Hospital in London where we are being treated, that means: "No narcotics. Minimise - or better yet, quit - smoking and drinking. Avoid hot baths, wear boxer shorts instead of tight briefs, and supplement your intake of vitamin E and zinc."

But there are much worse things than masturbation becoming a dreaded obligation. The spontaneity and carefree abandon that energise a healthy sex life are easily lost to the meticulous, obsessive planning that can hijack your relationship. The passion that my wife and I shared whenever the desire filled us was naturally regular and fulfilling. But a ripe, unfertilised egg waits for no man, and making love when the time is right can become a calculated chore, a looming necessity, bereft of the usual love, passion and fun. Like many men in my position, I have found it increasingly difficult, often impossible, to "rise to the occasion". I feel like the clapperboard has caught a key part of me when the biological director screams: "Action!"

Forty per cent of men in similar circumstances will learn that they are the reason that there has been no conception, which can be the psychological equivalent of castration. Counselling services are available to help men come to terms with their condition. But many, being men, suffer in silence or worse, inflict that suffering on their relationships. "The change is palpable," says Antoinette Johnson, a clinical fellow at Guy's. "One moment they are confident; then when they get the results showing that the problem lies with them, their whole manner changes - their look, their attitude, even their voice."

I was lucky: my samples showed an average profile of sperm: the majority depressingly malformed or immotile, but overall clinically numerous and able-bodied enough to fertilise an egg. My wife's diagnosis was similarly positive - normal hormone levels, a regular period and a healthy uterus.

Fertility treatment is costly and only a quarter of cases end up covered by the NHS. Funding is dependent on a number of controversial factors, such as your postcode, health authority, and your partner's age (my wife turned 39 the week they recommended this route, then added that it was only free to women 38 and under). Britain has an appalling policy on the financing of fertility treatment, shameful compared to other European countries, and there are few signs of this changing soon. Each cycle of treatment, which typically run in threes, can cost between £400 and £1,800, plus drugs costing up to £1,200.

We have now completed our first round of intra-uterine insemination, or IUI. It involves the woman self-injecting hormones to stimulate the production of several eggs, rather than the usual one in normal ovulation. The man's ejaculate is washed, spun and the ablest are concentrated for a strategic injection high in the womb. While this entailed more humiliation for us both - and again, more for my wife than me - at least this time we knew that it was all to produce two or three healthy ova in one go, set them on their way and then place my concentrated Olympian sperm right in their path.

After a series of progress scans, we were told which day insemination would take place. Thus another day of reckoning. That morning I had another go at filling the plastic tub. Several hours later, my wife had this prepared solution injected into her. It obviously involved far more pain and anxiety for her than the worst I had to endure, but 10 minutes later it was over. Hopefully X would meet Y, fall in love and divide their time together. It was time to get dressed and return to work, the insemination complete. No chance to roll over, light a fag and ask how it was. Although we don't smoke, it would have seemed more natural.

Unfortunately that cycle failed. A home pregnancy test broke the news in a most clinical manner. My wife's period shortly after confirmed it. While that was devastating after investing so much hope, emotion, time and effort, it brought us closer together, which was a fortunate consolation.

We are now about to begin our second attempt at IUI. Perhaps the second time round it will feel more natural, with my requisite masturbating on cue and our sex life benefiting from a more seasoned performance.

The possibility of having our own child is worth 1,000 encores.