Hay, that kind of pain during pregnancy can be tricky, please check with your OB as soon as you can, sis, especially since it's sudden. Could be maraming things, at hindi ako makakatulong properly sa online lang. Pero habang naghihintay ng appointment, try to stay hydrated and rest when you can (I know, easier said than done when you're six months along, diba?). If it gets worse or you feel anything concerning, go straight to your clinic or hospital na. Take care of yourself!