It is me? or is it normal?

this may be TMI but I keep worrying about it! Im 37 weeks pregnant and my husband isn't into sex anymore like he hasn't tried anything in like three weeks and when I go to initiate he tells me he's too tired and he'll just go down on me. We went from every other day to nothing in like a week! idk what to do he says its not anything about me but I don't believe him!