I've had pains for a couple of weeks now, (I'm 15 weeks). It's most probably round ligament pain as well as other stretching/muscle pains. However, if you're anxious, nervous, or just uncomfortable, you should call your health care provider. I'm a nervous Nellie, my doc is basically on speed dial.
Im 18 weeks and am experiencing the same pain. Its round ligament stretching. Its to accommodate the growing baby. Buy a maternity belt it puts less pressure on pelvis and also sleep with a pillow between your legs. Hope this helps