Nic, if that pain doen't settle, get it checked again. It more than likely IS constipation, but if you havn't had an ultrasound scan, they can't say for sure that it's NOT the dreaded gallstones.
If you're still in pain tomorrow and it's going through to your back, see your GP again. If it gets worse or is continuous, go to A&E and get checked out. (but I bet you settle down OK)
heres hoping you'll be better tomorrow.xx