You might have a little ulcer or low acid or any number of other issues. Food specificity may only be a dead end. Seriously, find a good gastric expert right away before you become malnourished, etc. beyond repair.
Steak, eggs, potatoes - fruits, nuts, berries and forage. Coconut milk and potent herbs and spices. Tea instead of coffee now and teeny amounts of kelp daily. Let's see how this does! Not really had dairy much, and gut seems better for it.
A simple meal of 3 eggs, 2 tablespoons butter, and 8oz steak, eating 2 times a day might work. I have found that Japanese Sushi rice is a safe food too. I use probiotics for Kirkman Labs. This probiotic is very good quality: The KIRKMAN Labs -SuperPro-Bio
Lactobacillus Acidophilus probiotics might help too. They are cheaper.
I am on the keto diet. I eat a lot of butter and coconut oil. Coconut oil has MCT oil in it. This contains caprylic acid with is able to kill some bacteria and fungus in the intestine. A person can buy caprylic acid supplements. Caprylic acid - Wikipedia, the free encyclopedia