Does the pain come in waves or is it consistent? If it comes in waves i would try to time the build up because you could be having contractions. I definitely agree with the above. I would contact your Dr office immediately or call over to labor and delivery, see what they suggest. Good luck
Have you called your doctor yet? It might be pre term labor and you should probably get checked out to be sure! Better safe than sorry but I would call them asap and tell them what is going on. Good luck!