Braxton hicks and contractions

Marie
I'm confused because I feel a tightening in my stomach (all over) and I'm 31 weeks at this point. I've had 4 braxton hicks contractions over the last 3 days. This recent one felt rather painful and the others aren't very great feeling either. Are they supposed to be painful? What do real contractions feel like? I always thought I'd feel them in my cervix? I'm so confused...