Labor pains??? Help!

I'm 34 weeks 2 days FTM I was sitting down for lunch break at work then all of a sudden I got a bunch of lower back pain that is persistent. I've taken Tylenol and used a heating pad and I'm still having a bunch of back pain. I haven't experienced back pain like this before and I don't know if it's normal. My OB doesn't have an after hours number. I really want some more advice before I just go to the hospital and make myself look like a fool for them to tell me it's normal 😳