You could be in labor if you had your last one early.
I have 4 kids and am currently expecting number 5! My best advice is to see a chiropractor asap! Back labor will only get worse with time and it is caused from the babies spine touching your. They can help move her/him into a healthy position and get ready for delivery! Drink plenty of water! Good luck!
U may want to go anyways or try calling the ER to c if maybe they can tell u whether or not u should come in...idk if they will answer ur question but if they do, it saves u a trip.