Help!

I'm writing this anonymously because I'm mostly embarrassed. Ever since i Found out I was pregnant I just don't have the sex drive anymore. I'm always tired and just never in the mood. My fiancé doesn't understand. Before I got pregnant we had sex constantly. Now it seems we fight every day because I'm not in the mood to have sex. Anyone else going through this? How do I get him to understand what I'm going through and the physical changes im dealing with? I love him more than anything. But it's frustrating because he won't even consider what I'm dealing with physically. I'm now 10 weeks pregnant. Any advice on how to deal with this?