CC - yes, cramping is completely normal. I had such bad cramps with DD between 6-10wks that I would sometimes have to lay down and curl up in a ball... I asked my OB and its very normal, especially if its your first or you havent carried a baby to term then the first time your uterus grows that big its going to be a bit sore. As long as there is no blood and no terrible lower back pain with it then it's probably just stretching pains. When you go to the gym and use muscles that you haven't used for a while afterwards they cramp and hurt... Same with the uterus.
I hope this helps a little?
Oh, and my boobs aren't as sore the last 2 weeks either... Or I am just getting used to it and don't feel it as much?!