sexual rejection

My now fiance and I have been together almost 2 years now. And it seems that he has no interest in sex with me. In the beginning we did have sex 3-4 times a week.. but now I'm lucky if we even have sex once every 2 weeks. I try and arouse him, I give hints.. I've even been blunt to get him to have sex. Every time he rejects my advances it feels like he doesn't care. I cry sometimes after he rejects me. But then anytime he is really in the mood, it is suddenly okay to have sex. and when I try to ask/ talk about why we only get sex when he wants, it turns into an argument about who is in the wrong. I cant get the thought out of my head that I'm either not good enough, or I'm not the only one in his life. Which makes it harder to keep planning my wedding when I'm now not even sure if he even wants me anymore.

Talking to him doesn't do anything. So what can I even tell him? when I bring up my emotions about rejected sex he may reluctantly then have sex. But then I don't even want to have sex anymore because he ruined "the mood". I'm at a loss. We were going really well too. We were trying to see if we could conceive as it would be both of our first child.. now he just doesn't care. Help!