Braxton hicks contractions? Worried.

Ts
Last night, I noticed some cramping, and people told me it could just be Braxton hicks contractions. Today, I still have this uncomfortable feeling. I don't know whether it's a contraction or not. It kind of feels like I did a bunch of crunches, and now my stomach and abs are sore. It doesn't feel like it comes and goes either, more like an all-day pain. I've called my nurse, but no response yet. I'm 26 weeks along. What do contractions feel like? Did this happen to you? I dont want to go into pre-term labor!!