Hey girl,
I experienced them when I was 13 weeks with my first child. I went to the hospital and everything. As long as the cramps are bearable and there is no bleeding, your fine. It's your bodies way of saying hey your preparing yourself for a baby! Breath :)
BH to me don't hurt they just tighten.. Contractions feel like worse period cramps and I also had really bad backpain. If the tightening is time able.. I'd go to L&D just to make sure every thing is okay