Lack Of Sex Drive at 37

I don't know what's going on with me. I'm so not into sex lately. I feel like I have to force myself into wanting it. I can't figure out if it's me or my boyfriend. He's 41, a diabetic, and it seems like he wants sex all of the time. I don't. I work. I'm a mom. And I'm always exhausted. I truly don't know what to do.