I seriously overindulged yesterday (special occasion). Got a burning around my diaphragm, which I presumed was indigestion/reflux. Took some Rennies but they didn't help.
The pain got worse and when it properly developed, it was actually slightly to the right of centre, under the rib. It was a constant burning/stabbing pain. Eventually went to bed and by this morning it had passed. Today I've eaten very sensibly and it hasn't come back.
In the past, when I've overindulged, I have sometimes got a sort of 'stitch' on the right side, but never this.
I'm slim and healthy (though prone to the odd overindulgence) but there is family history of gallstones.