You could be having back labor. If it continues, go to the hospital.
I'm 37 weeks and have the same problem. This past Saturday I finally just went in to the hospital and they said I was having contractions 8 min apart but because I wasn't dialated at all they basically just told me to deal with it and sent me home. Unfortunately there really isn't anything they'll do for you at this stage. I've just been taking hot baths and using my heating pad. It doesn't help too much but it's about all you can do. Try a hot bath and then if that doesn't help at least a bit then go get checked out at the hospital but don't get your hopes up that they'll do much. Good luck!