"Growing Pains" or what?

So I am 21 weeks as of yesterday, and the last 2 nights and this morning my abs/stomach hurts like I just had a super good workout.. It's not hurting right where baby is, it's more in my rib cage area and sometimes down both sides (if you move just right). As a bonus, I can definitely tell my uterus is growing/stretching....is anyone else experiencing this type of soreness?