Pain during sex?

Hey all! I have been with my fiancé for almost 3 years now. We have a good sex life and never have any problems. We are not really "trying" but also not preventing.. Anyway, the other night when he finished he kinda pushed himself further inside me, which he has done before and I usually like it, but this time it made me scream in pain.. It made my whole uterus area tense up. I felt a lot of pressure like I had to pee ( I didn't FYI ) and it took about 10 mins for the pain to stop..has anyone ever experienced this? I'm just curious what it could be.. It might be because AF is close but I can never really tell since I'm not regular.