33 weeks 2 days. . contractions !!!???

I'm up its 1 :00 a.m where I live and I'm in bed then I began to have period like pain. I layed in bed rocking my legs back and forth as the pain came and subsided . its now gotten a little worst with back pain. I went to empty my bladder in hopes of it just being BH but then I had diarrhea and as I just came to lay back in bed the pain is still with me . could this be the start of real contractions ? When should I call my doctor? I don't want to seem dramatic if its nothing