Pain in Abdomen: For about a year now I've on occasion experienced a very sharp pain...?

in my abdomen, just to the left of my belly button. It was always when I had been setting cross legged with my left foot under my right thigh. I just thought it was a nerve thing. Recently I've experienced the same pain while standing and/or lying down and I'm starting to worry. The pain is extremely sharp, enough to practically take my breath, but fleeting. If it continued for more than a nano second I'd be on the floor writhing in pain. Does anyone have any ideas as to what this might be?