Hello, I would be happy to help.
This is likely related to the joints in your pelvis. The pelvic bone represent five bones fused together. These joints become more unstable in pregnancy
. The fact that the cracking and popping is clearly related to position change, then this is the most likely explanation. It is of low concern if this is the cause.
If you have persistet unexplained pelvic pain
, though, you should talk with your OB/GYN.
I hope this helps.