Pelvic/pubic popping and cracking when I sit up after laying down at 33 weeks pregnant?? it's not…

Pelvic/pubic popping and cracking when I sit up after laying down at 33 weeks pregnant?? it's not extremely painful, it's actually quite bearable, just feels weird I guess. I go to the doctors for my 2 week checkup on Tuesday but I was just wondering if anyone experiences or has experienced this and what it is??