i think i'm having contractions

well i'm gonna ask my doctor to be sure, but i think i'm having contractions - not like regular i'm-in-labor contractions, but just random getting-ready-to-really-do-it type contractions. they happen in my back, but they aren't radiating around to the front like i read they're supposed to, so i don't know if that's really what they are or not. it's happened maybe 3-5 times in the past week-ish. it happened again today about an hour ago or so. i was peeing (tmi, i don't care) and all of a sudden it started in my back and just hurt so bad i thought i was gonna fall off the toilet face first. i couldn't think of anything other than how would i get my pants back up if it didn't stop hurting... and then it went away after like 30-45 seconds. it was terrible. i'm terrified. if labor feels like that then oh my god. i can handle cramps and pain in the front/lower area of my pelvis all day long (like where normal period cramps hurt) but i'm a back wimp in a big way... oh man oh man oh man scary. we'll see what dr. stack says tomorrow.