I’ve been engaging in random sex with people I don’t really know for about six months. Recently I met someone on one of these casual encounters and we both decided that we quite liked each other. But now that he’s my boyfriend, I find myself unable to maintain an erection. Foreplay is great but as soon as we get to sex I lose my erection. He’s the first person to ever mean something to me.

It is possible that you have a sexual problem with either desire or arousal, or even depression, and that you have been unconsciously trying to correct this via the eroticism of random sex. But it is more likely that intimacy – getting psychologically and physically close to someone at the same time – is a struggle for you. This may be why you have previously chosen not to have a boyfriend.

It may be that you are growing more capable of forming a bond with another person, and this could be a wonderful but challenging new step for you, so try to be patient with yourself. It could be useful to discuss the issue with him – it is a pretty common problem and I doubt it will faze him.

What is most important is the erotic spark you manage to generate together until performance pressure (or fear of intimacy) puts you off. Try to avoid that pressure by elongating foreplay; you might find it turns out to be the main event. As intimacy becomes more comfortable, things should improve.