Please Help!

I purposely didn't go to my last appointment with specialist where she would b doing nst every 3 days bcuz I waited for 4 hrs to be seen by her. I thought I'd tell my OB that i didn't want to see her. im 34 weeks and I've been having period-like cramps and back pain for a few days now. I'm not sure if I should wait to see my OB tomorrow or head to the ER since I hear this could be pre-term labor. I'm hesitant because OB is going to be angry that I didn't keep my appointments with the specialist. any advice or opinions will help. TIA