How did things turn out for you? I am 53 and have almost the same identical situation as you: Runner, ultras, healthy lifestyle... etc. I also have the constant, painful belching and gas with a bloated abdomen. A few weeks ago I belched throughout the entire course at Stump Jump. :P The only other health issue that I've had is breast cancer 2 years ago. But my belching started before BC, so it's NOT from the stress of cancer treatment.
HI my name is Berry. Did you ever find a cure? My sister has the same problem and has no idea what to do. The Dr's are lost. Please let me know. My email is ***@**** Thanks Berry