how often do you have sex during pregnancy?

Are you still having sex frequently during pregnancy? My husband never seems to rest... always asking for it almost every night. He says he's "saving up" before we have to stop after childbirth. Honestly, I'm tired, but I feel bad rejecting him. Sometimes my stomach cramps, but my husband promises to be gentle. I had a little bleeding once, but when I checked with the doctor, everything was fine, and I was advised to rest. After that, my husband asked again. How often is it actually okay to have sex during pregnancy?