It is very common for difficulties in conceiving to cause sexual problems due to it all getting railroaded by the mechanics. It is vitally important that you get back to making love rather than making babies. This might involve prioritising making love at times when you are unlikely to conceive so you can concentrate on the passion! Don’t allow your love life to be turned into a purely functional operation, with legs raised after ejaculation and other tricks; it is much more important that you stay entwined in intimacy.

Since you describe yourselves as not having had a sex life for so many years, I would recommend you rebuild it gradually. Start with the basics, enjoy some foreplay with the agreement that it won’t lead to intercourse so that you can rebuild some sexual excitement, anticipation and fun. With this as the goal it won’t matter if you keep a firm erection or not. Talk about what type of touch or positions you enjoy the most and try some new things. 

Reading between the lines, my hunch is that this is not the only mental passion killer for you and that quite understandably you are ambivalent, if not downright scared, of the thought of going through labour again. This is a hard one to own up to when your wife is so emotionally driven by having another child. I have known men to find it easier to own an erectile dysfunction than to face the mountainous conversation about not wanting to conceive. 

You need to recognise that you too went through a traumatic experience at your son’s birth. The most primitive instinct of a man to protect his woman will be triggered by childbirth and when he is powerless to do this, with the medics taking over, he can easily go into a traumatic shutdown reaction. Until he can process this trauma openly he is never going to wilfully put himself back into the same position again. 

It is time for you to face the real conversation about that birth and your feelings about having another baby. You may need to do that first with a trusted friend or counsellor, but in time you will have to put it together with your wife. 

Another question I would want to ask you both is to look at where you feel in the pecking order of the family. When a new baby arrives, men often feel they go to the bottom of the food chain, which they can live with for a few weeks or months, but not for longer. Have you returned to feeling head of the household and that this family is run by two equal lovers? If you still feel you are at the runt of the pack, you are unlikely to want to add another competitor! 

As for Viagra, it will not work where the desire for sex is cutting out. It cannot give you that; only you can contribute that vital ingredient. I am pretty confident that once you have made peace with the issues above and found your way through them together as a couple, that you will find that your ability to sustain an erection and to ejaculate will return. The problem is not the problem; the problem is in fact an inadequate solution. 

Maggie Ellis is a psychosexual therapist and director of the charity Lifecentre.