On my right side, immediately to right/above my belly button. Sometimes when i slouch down on a chair I get a sharp numbness in this area when I start to sit up and it gets rapidly worse when I sit up normal and usually lasts for up to minute then its gone. It hasn't happened outside that circumstance. It almost feels like its going to explode. Slight unnerving. What could it be? I'd say it first happened 4 years ago. Thanks