On eating bread/wheat products -
A dietitian once told me that some sensitive people find their body copes with it best at midday, and if it is also recooked - that is - toasted.
Also - the how much how often question. A tiny bit once in a while might not upset as much as opposed to more, or more often.
The type of cooked wheat product might be part of the equation, and also what else was eaten around that time.