R.S.
Some women experience round ligament pain during pregnancy.
This is your first pregnancy, I am guessing? I would strongly recommend that you really call your doctor first for anything. Mamapedia is great, but IMO should never take the place of a doctor's advice, ever. We are all nice people and well intentioned mommies (and occasional dads) but truthfully you don't know any of us. If it were me, I would not take medical advice from strangers who cannot even see you, much less examine you.
Should you call your doctor? YES, and now.