Back pain.. prodromal labor or musculoskeletal?

Yesterday I walked around a bit, but no more than usual and I've been having lower back pain with mild cramping since. It went away after falling asleep last night, but after getting up and moving around a bit today it's back and it is super uncomfortable. I can't tell if it's coming in waves or constant, but movement doesn't relieve the pain and resting isn't helping either. I know I'm not dehydrated.

I've called the doc and she said to try to wait it out because she isn't sure if it's musculoskeletal from looser ligaments or pre labor. This is my third baby and I'm only 36 weeks 2 days.

Not sure if I should just go in and be checked or wait for the pain to increase?