Help! Low sex drive.

Long story short, I'm never in the mood anymore. Nothing gets me in the mood. Its making my fiance depressed because I just don't want to have sex and he wants to have sex all the time.

I have ocd, depression, and anxiety, if that makes any diffence. Its not that I don't love him, I just don't want to have sex. He tries to get me in the mood but all it does is annoy me because no matter how many times I tell him I'm not in the mood, he keeps trying and trying. It makes me feel like a bad fiance but I just.. can't help it. I have no control over it. I try to get myself in the mood but nothing works. I don't know what to do.