Ok idk if that's the proper way to describe it but basically when I'm having sex with my boyfriend I'll feel/hear a popping inside of me. And its like every thrust I'll just feel a small pop. It's not painful (feels similar to when he's fingering me and his knuckles pop inside of me) and sometimes if we change positions it'll go away. My first thought was either him hitting my cervix or maybe just an air bubble or something. The air bubble theory seems more likely to me since it goes away if we change positions