Air Bubble During Sex

My boyfriend and I were having sex and there were a lot of air bubbles coming out, almost like my vagina was farting around him. I asked him to stop because as he was moving deeper there was a lot of pain, as if someone was blowing up a balloon inside my vagina. I've never had that happen before and it scared me. After a few seconds we switched positions and it didn't hurt after that. I didn't feel anything pop or bubble after I moved to a different position so I'm wondering if there is another reason it hurt and/or stopped hurting. If anyone has any advice it would be really helpful. Thanks