Right. So you've been together for six months, and besides the fact that the sex is rubbish and you can't communicate with him, everything else is going really well. Hmm? I'll be honest with you, it's not looking good. Basically, if you can't bring yourself to talk about sex with your boyfriend, then you shouldn't be having sex with him. Or anyone else for that matter. Lying back and thinking of England has been over since about 1964, and I can't believe no one ever told you what a lousy success rate telepathy has.

Even in 2009, some men just don't get the subtlety. Unless they receive clear, concise instructions - you know, “up a bit, down a bit, a little bit softer, ouch” - they just autopilot towards ejaculation.

Evolutionary geneticists would say you are correct to label that as “selfish” sexual behaviour, but the 21st-century male can truly be described in that way only if he ignores his partner's pleasure to satisfy himself. Your boyfriend is not doing that. He is simply failing to figure out what you have neglected to tell him.

Yes, yes, if he was some kind of New Age love guru, he might have pressed you for more details as to how you like your yoni tickled, but first he would have a beard, and second the average Joe is even less equipped than you are to broach a topic of conversation that has the potential to leave him feeling rejected, foolish, awkward or inappropriate.

Presumably when you first met your boyfriend he could do no wrong, and although I doubt his sexual technique is any different, six months later he is a selfish lover. What has changed? Could it be your perception of him?

During the first flush of romance, it is normal to idealise all aspects of a relationship, but your reluctance to express your sexual needs inevitably means they don't get met, and that sets a predictable cycle of dissatisfaction in motion. You won't tell your boyfriend what you want, but you will blame him if he doesn't guess right away.

I'm not excusing his insensitive behaviour, but to change this relationship, and indeed any relationships you might have in the future, you need to take responsibility for your own sexual pleasure and become more assertive. Rather than dumping him, dump your inner April Wheeler and embrace your inner Samantha Jones. And if you like this guy, try not to humiliate him in the process.

The key to successful communication is to avoid coming across as hostile, critical or contemptuous. Or in the words of Bing Crosby: “You've got to accentuate the positive, eliminate the negative, latch on to the affirmative, and don't mess with Mister In-Between.”

The relationship guru John Gottman suggests that when you have to have “difficult” conversations with your partner, you should think of every statement as “a fork in the road”. Each time you have the opportunity to say something, you have a choice: keep your discussion reasonable, or allow the conversation to intensify into something more destructive.

The ego can be incredibly fragile when it comes to sex; if you blurt out that you haven't enjoyed the sexual side of your relationship since you met, your boyfriend will be crushed. But tell him what you do enjoy in bed and he'll be delighted.

Even if you find it hard to express yourself vocally, remember that actions speak louder than words. Appreciative noises when he does focus on you and get something right are a very effective way of communicating your needs.

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