Popping sounds!?


So baby number 4, 28wks, he is moving fine no severe issues other then pelvic pain and feeling like I’m carrying a bowling ball between my legs.. but recently I’ll be sitting and hear these popping, almost knuckle breaking, sounds from my belly... anyone else have this going on? I don’t remember it happening with my other children.. and I’ve only had my water break once, and that was with my first 5 years ago... anyone!??