Since you mention some foods causing irritation, it made me think of the Blood Type diet books.

Like Eat right for Your Blood type by Dr. Peter D'Adamo
The book is in libraries & usually can be found in thrift stores too.

I found foods to avoid and many were ones that were giving me tummy troubles. Also suggested foods that are good for your type.

I don't fully follow the plan, maybe I should LOL.
It does seem oddly coincidental that the bad foods listed for my type are the ones that give me some problems.

Maybe this sort of thing will be helpful for you.