I Have An Intermittent Ache/pain Below My Bottom Right Rib,

I have an intermittent ache/pain below my bottom right rib, close to the center/solar plexus - almost like a stitch in my side, but int he wrong place, and not quite as sharp. It tends to occur if I've been sitting for extended periods in front of the computer (like now), or sometimes after eating a large meal. Ideas? Changing positions (by standing up) semi-relieves it, but not entirely.