sounds like you do have an allergy so you might need to make your own cereal and just not put oats in it.. I have a vegetarian friend and she swears by quinoa so I guess you could mix in some flax seeds and other nuts and see how you go with that? What about cream of wheat or rice? I get all bloated from wheat bread so I switched to spelt and I'm fine now.
I guess you could start out with really small amounts and see what happens-that way you'll know if you can't have any at all or your body may adapt. I'm not sure whether it will go away completely but you may be able to build up a degree of tolerance over time.