Low Libido and hating it. 😞

So I am almost 38 weeks pregnant and since about 20 or so weeks I have not really wanted to have sex with my husband AT ALL. There's been a few rare times that I've wanted to do anything at all. My husband is pretty understanding about it although I know he gets irritated. I just don't know why I feel like this. Like I WANT to want to have sex but I get this "don't touch me" feeling most of the time. Shouldn't my libido be up right now?