I wait tables twice a week for a little extra cash. My shifts aren't particularly difficult or long, but I am on my feet walking around for about 4ish hours.  After about 2 hours my belly starts aching. Sitting down on the way home is uncomfortable, but the standing BACK up out of my car and walking is awful!!!  It feels like my stomach muscles are extremely tight and it's really uncomfortable moving. Does this happen to anyone else?