Period like cramping and pressure...

Ivy

I'm currently 33 +3 And I've been having very uncomfortable period like cramping mainly at night and pressure. I tell my OB all my symptoms and I feel she doesn't listen to me at all. She keeps saying its normal and the day before yesterday at my appt she said that my "Uterus is tired"?? idk what that means but, should I prepare myself for a preterm birth just in case? It's too late in my pregnancy to find a new OB and I have about 6 weeks left but definitely dont feel she's gonna last til then. Anyone else experience this?