I had a similar pain around the same weeks It was my ligaments stretching. Go to the E.R. to give yourself some relief but this is baby # 5 and it was new for me. I hope you feel better.
If its extreme, I would head straight to the e.r. if I were you... I'm not sure what it could be, not to sound down but when I miscarried I had no symptoms until 2 weeks later when I started bleeding. It may be gas or a trapped bubble, but like I said, I'd go to the e.r.