That's no fun! Sounds similar to what I was like a number of years ago. I would eat a meal and an hour later was running for the toilet. Rather nasty condition as I was always hungry.
My guess is the pills you are on are causing stomach issues. You might talk with your doctor to see if there are others that can be tried. Maybe the drugs have disrupted the healthy probiotics in your colon.
I've had better luck with over the counter imodium verses pepto. As for diet, you might try taking wheat and other grains out of your diet for awhile and see if the situation improves. An article I recall about wheat and colon health ~
"The Battle for Control of Your . . . Colon" www.wheatbellyblog.com/2011/08/the-battle-