I had this for several weeks around the 20 week mark. Dr suggested it could be a hernia (which it wasn't). I read lots of books & internet articles & no one seemed to mention it as a pregnancy symptom - but it can really hurt huh?

Anyway, I found that I was sorer when I had been really active during the day & used ice packs on days when I was really sore. I think it was probably just from my belly stretching - it is my first & I was not that big to start with It got better after a month or so, once my belly was stretched I guess!