It’s best to rotate all of your food items so that you don’t become allergic to anything in particular. This also helps keep the yeast on its heals because it continuously has to adapt to your diet. This also will help with your nutrition because there won’t be anything you are particularly deficient in.
Since oat bran doesn’t work, I would try out millet, teff, or maybe make soup for breakfast, etc. Cream of rice is another option.