Yeah that's what's happening. Your bones, tenants, and muscles are all relaxing and can even dislocate to prepare for bitth. 2 times i had my tendant between my thigh and pelvic bone dislocate while i was walking in the store and i couldn't walk. Randomly 20 min later it "poppped " back into place.
I was having some popping yesterday and talked to my physical therapist about it. He said due to the relaxin hormone that everything is sort of shifting around getting ready for delivery so its normal to hear some popping.
Mine does that too. Im 38 weeks 3 days. I think its cuz your body is trying to loosen up for labor.