Pressure under right rib cage (Read 34 times)

I'm a 59 year old marathon and ultra runner with over 30 years of distance running under my belt. Three years ago, I developed a strange feeling of pressure, almost like a balloon inflating under my right ribcage during and after eating. My gastroenterologist, thought it was being caused by irritation to my colon. He prescribed my a mid antidepressant, Amitriptyline that also has a calming affect on the colon. This worked. Over the past month, I began to feel the exact same sensation when I run over 5 miles. I asked my gastroenterologist if increasing the dosage would help. Since I'm experiencing only during exercise, he doesn't believe it's digestive related. Wondering if anyone else has experienced this odd feeling, no pain just uncomfortable pressure.

Thanks for any help, John