Muscle aches on right side??

Kimberly🚮🚮😘 • Momma to Orion, Taurus, opinionated (sorry)
I'm 17+5 and especially at night when I lay on my right side or back I'll wake up with a muscle ache on my right side right above my hip, but it's on my back. We say baby boy a few days ago on ultrasound and so we know everything is ok, but what could be causing this? It usually gets better after I get up and use the restroom