If you were totally satisfied with your ex, you’d be staying put and working at any problems, so you could avoid the stressful on-off-on-off pattern. Which leads me to another point: do you find it stressful or exciting? It might be the drama of the break up and get together that appeals.

Don’t feel you have to identify yourself as being either straight or gay – it’s perfectly OK to be bisexual, and this does not mean that you’re ‘sitting on the fence’ sexually, or that you’re greedy!

If the roles were reversed and you were married to your younger friend and your husband was untried territory, I suspect he’d be more appealing.

Our drives are most similar in the early lust-filled stages of dating, when Nature is pumping our bodies with chemicals to make us mate and bond. But once that bonding has taken place (usually within 2 years) then the drive tends to drop.

It’s not particularly designed for long-term use. Instead, it’s supposed to get you to the stage where you can recognize the point of ‘ejaculatory inevitability’: when it’s all over bar the shouting.

It’s always tricky dealing with mismatched libidos. If you have a low sex drive and your partner is the opposite, you may feel pestered to have sex when you aren’t in the mood, whereas he feels rejected.

Your husband has the right idea making moves now. He figures you’ve done all the hard work bringing up the kids, now it's your time to enjoy yourself. And what better way to enjoy yourself than to have sex!

It sounds from your letter as if you’re not only missing this element of your love life, but that you really care about your partner’s welfare, so I hope this will help with both.

He probably uses it when you’re not around and he feels aroused. Or perhaps his libido is higher than yours and he’d rather take care of himself than hassle you for sex when you don’t fancy it.

I can understand your frustration, especially as you have tried talking to her about the situation, but how about now diffusing the situation entirely and just offering whatever support you can – especially with your kids?