Have you tried simple food separation? If you're going to eat meat, just eat meat. Or if you want to eat vegies, just eat vegies. Same with fruit...
The theory is that it's easier for your body to digest one food item at a time.
Fat's, Proteins, Meats are okay to eat together.
Vegies by themselves avoiding the food items that are hard to digest anyway, like corn.
Fruits by themselves
Avoid all grains (yes even whole wheat)
Avoid bread like the plague
Avoid as much sugar as possible, this means reading labels on everything you buy. (except for fruit, eat all you want)
DO NOT AVOID FAT.... low to zero fat items always have additional sugar to make them taste okay. The fat is better for you than the sugar.
And the absolute worst item a human can consume? Doughnuts.... Bread / Carbs mixed with sugars and mixed with fat.
The separation thing has helped my wifes stomach problems greatly.