Depends. Could be labor. However, more than likely it's simply the pressure that comes from having an increasingly large load pressing down on soft tissues in the pelvis that are not usually subject to that pressure. Also, pregnancy doesn't protect you against the same stomach problems we all get from time to time. In any event, you should see your obgyn or go into your hospital's triage for evaluation.
Please CALL YOUR OB. Asap, not normal u could be going into premature labor or have other problems, call your OB now or go straright to the labor room if u do not have an OB or teh OB does not call back.
Lower abdominal pain. Lower abdominal pain during pregnancy can be due to a number of factors including urinary tract infection, premature labor, gastroenteritis and others like round ligament pain (if it is one side). You should see your physician right away for evaluation to determine the cause.