39 weeks sex.. normal?

I'll be 40 weeks this weekend. My husband and I were having sex last night. I was on top, then we switched and he was on top. After a while he said he couldn't put it in deeper. He said he felt something blocking and jumped off me. Lol he freaked me out but i told him it couldnt have been the baby bc she's in the amniotic sac and to try a different position. So we were on our sides, he puts it in and say somethings still blocking. He took it out immediately and was freaked out. We didn't even finish ☹ We were fine when i was on top and the first few minutes he was on top. We were thinking maybe the baby was pressing down, idk?! Anyone else been in this situation? If it means anything, the beginning of the week i was 3cm dilated & 80% effaced.