Help?!?!?

Okay so just a minute ago i got up from laying with my son while he took a nap. Well when i sat up my stomach felt really awkward like my son was in a very awkward position. But i got up to go pee and i thought while i was peeing i had to poop. But then all these pops happened in my lower back. It felt like air bubbles poping? Now one side of my lower back hurts. Know what it could be? Im 38 weeks.