Much of feeling something, including between your legs comes from feeling stuff between your ears. Do you, or have you any of those feelings for your man? Not just love, but attraction, and ..there are so many. You also must feel something for/about yourself, and in the relationship. Especially for many women, sex and feeling something is not just stimulation of the sexual organs.
Also, if you take medications, some of these often tend to be a problem.
Then, of course there is your history, your health, your past experiences and health, and psychiatric stuff, and abuse issues.
You are asking a very big question that could have many, many causes, and I think you know deep down more than you think you know?
have you trid consulting a Dr about this? luck jo