My advice is to do whatever it takes to fix it. Talk with your OB/GYN or other doctor to rule out hormonal imbalance, and/or seek counseling. This situation isn't healthy for either of you and if it continues, I'm guessing you won't be living the rest of your life together. Unless, of course, he's okay with never having sex again. And a wall of anger will build up between the two of you. You, for having to have sex with him, and him, for knowing you don't want to. In all sincerity, good luck!