Obviously nobody wants to take a guess and try to help you, I know that once you get closer to the end of your 2 trimester/ beginning of your 3rd trimester your muscles will be sore from stretching so much. It could be that, just I think if it was that it should be in the bottom of your abdomen, but you never know. You might try going on www.webmd.com and go to the system checker (there is a link about half way down the front page). Hope this helps you!!!! Good Luck!!