you REALLY NEED to see what is called an integrated medicine doctor. You will not find them at Mayo or at your "normal" allopathic doctor's office.

It appears there are many people who allopathic docs simply are not helping / understanding when it comes to GI issues.
search: "ifm"

Do not waste your time any longer.
But get ready to pay cash on the order of $300/hr for their services-- very few(virtually none) will take insurance. Still, don't just trust "any" one of these. First one I tried after spending over $500 for his "time" and $800 on specialized testing wanted me to take 960 pills in 30 days to start to solve my problem.
Another route: find a nutritionist or dietician through other alternative med clinics like a chiropractic office etc. That is what I am doing.
Finally, read up on "SIBO" and the "elemental diet"
It makes sense, at a minimum, to get tested for SIBO(specialized stool test + aerodiagnostics company or equal breath test)

search terms:
SIBO info
hollywood homestead
digestive health institute

Finally, good luck.
This will be a long quest. However, I have just saved you some time IF you follow up.