Irritable Uterus

Question for ladies that had/have an irritable uterus: 
I'm a FTM, 37+3 today and my typical IU contractions have been going on today but they've been accompanied by back pain slightly above my left hip bone. It sort of starts there and then I feel the rest of my belly get hard and tight for about 45 seconds. I haven't had back pain at all before today. 
I'll ask my doctor when I go in for an appointment this afternoon, but does anyone have experience with this?