Pulling lower ab pain while using the muscle. Help!!

So in the middle of the night i got up to pee (my bladder was extremely full) and a great deal of pain happened when getting out of bed/walking to the bathroom. Normally it goes away after using the bathroom but this time it didnt. Every time i move, shift, walk, pretty much contract the muscle that pain is intense. Is this normal? Baby is still kicking, i feel fine and no blood or anything. It literally just hurts when i contract the muscle. If the muscle is at rest i feel fine. Im 37+1 weeks. Should i call my doctor or is this a normal symptom as your get later in your pregnancy. Please help! This is my first pregnancy.