Ya know, I just found out I'm pg (for the 1st time) and every once in a while, I've been feeling that too. But I've also been doing IVF and have been on all kinds of hormones. Weird. I hope it's normal!!
Congrats on your pregnancy! First of all, how far along are you? I don't want to worry you but if you are before 12 weeks, you may want to get to your OBGYN and see if it's anything to worry about. Later in pregnancy, you can experience those type of pains due to positioning of the baby, how active you baby is, your baby could be pressing on a nerve or your bladder, causing sharp pains, and what-not. I hope everything goes well for you!
My doc said it was the muscles surrounding the vagina and uterus that are pretty much (to put it bluntly) "ripping apart" after awhile they do get better but at first it is quit painful. Nothing to worry about, i'm sure hun.