Frustrated, horny, & wondering why???

I have been with my fiancee for now almost 2 years. We had a miscarriage March 2016 and talked about TTC again. Well here lately it seems like he doesn't want to be around me. It's like he does everything in the world to not to around until midnight. We talk about having sex but then when it comes to it.... it doesn't happen. I've asked why. I've asked if he is cheating. I've asked if it's cause I put on just a lil weight. And he tells me no on all of them. He says he wants a baby. But when I am suppose to be ovulating it seems like he distance his self so much!!! I've even told him if we don't start having sex (and even forget the baby) I will cheat on him. I don't want to and I probably won't.... but damn I need that feeling back. Sex and mental loving back. What should I do?? I am so needing to be touch and loved!!!