Preterm labor?

Sammy
I'm 24 weeks tomorrow and for the past two almost three days I have had a sort of painful discomfort down there. It feels like the muscles on the left and right of my uterus if that makes since. It just hurts so much at times. I sneeze, take a two, go up stairs, or bend to pick something up from the floor, it hurts. Like its swollen or something. Idk what this is. I have an ob appointment Friday morning, but I don't know if I should call and be seen early or if I should just take it easy. Anyone know, or been through this?