Call Ur dr. But it's probably just Braxton Hicks. My BH are only in my lower stomach, mine are painful, & I never get back pain. I'm 34 wks prego w 3rd baby. But definitely call Ur dr let them know. And yes start timing them, if it's true labor you'll be getting them every 10, then 8, then 5 minutes and so on until they're about 1-2 mins apart. Also time how long they last. I think this app has a contraction timer or U can download a contraction timing app.
I'd suggest timing it. If its not consistant its not bad but if it is you need to get in a bath with a cup of Epsom salts in to stop the pains.