One of the things that crops up a lot in these forums is women that are with men that don't seem to want to have sex as often as they do.
Often women are attracted to these guys because they're sensitive and talkative and understanding. The women are often strong and confident. So what you have - frequently - is women with a very strong 'masculine' energy, and guys with a strong 'feminine' energy.
What happens then, is that in the sexual relationship the women expect men to take the 'masculine' role and when they don't, the women take it on instead.
Can you see what might happen?
Sometimes the guys retreat from being sexual.
I wonder, and it's just a thought, if you 'enabled' your guy to be more traditionally masculine in your relationship, whether, over time, the sexual dynamic would change.
Allow him to do every-day things for you that assist him to feel 'manly', don't ask him about everything he feels, complement him for the things he does (subtly, of course) and, don't nag.
It's sort of men are from Mars, are from Venus stuff, but there is an element of truth in it.