Hi Badger -
I'll go along with the others and just add a few tidbits.
You could be eating a bit too much. Your stomach is considerable smaller now than it was. Keep meals much smaller than you used to. It's a great reason to eat healthy.
Bread, wheat, make gas. This often causes stabbing pain in the large intestine. A loop of the large intestine comes up right under the stomach and it's really easy to mistake pain there for stomach pain, especially since the stomach has been moved during surgery. Pushing on it will hurt worse.
Booze, especially wine or fresh beer with live yeasty beasties, can do the same thing. Enjoy just a taste or you can get those critters fermenting anything that's down there.