Sharp pain under ribs

Today is my due date I'm exactly 40 weeks but still no sign of labor. Can someone help me explain how contractions supposed to be like? All I'm feeling now is tighten in my stomach and sharp pain under my ribs. Is that consider contractions? The stomach gets really hard and pain under my ribs. Last for about 5 mins sometimes less. It comes and goes. Sometimes I feel like I need to poop but I couldn't go. Please help??? When should I go to the hospital?