Last night I woke up to urinate but when i did, my bellybutton area started having a sharp pain and it has happened a couple of times before, but not too often. If this helps, I worked out pretty hard that same night about 3 hours before going to bed, and I did do a good amount of crunches. I would describe the pain as sharp, or almost like it's tearing. Its the type of pain that made me have to check my bellybutton a couple of times thinking it might have been bleeding from being torn open.