Help.. Concerned about what I am feeling in my stomach.

I am 29 weeks and 5 days.. Ok so this afternoon when I was on lunch I walked to my car and sat down. I had the weirdest feeling in my right side of my stomach like it was very tight inside there i even screaMed when I had that feeling it lasted for a couple seconds... I got the weird feeling again in my lower part of the stomach .. I do not know if this is normal.. Could this be Braxton contractions or could it be something serious ? It doesn't feel anything like when the baby kicks... When I do get the strange feeling I don't even want to move ... Has anyone went thru This?? I am going to the doctors tomorrow but for now id love to hear from you gals..!!