I know EXACTLY what you are talking about. I had it horribly with my first prehnancy, and then less with the second. At first I thought it was because I had broken that rib about 6 months before but it wasn't. The OB said it is not uncommon.

I wish I had a solution for you but in the end I just became great mates with my heat pack. I will try to think if there was anything else I did and if I can will get back to you - bub is screaming for a feed!