u might be allergic to a particular food or maybe the likes of bread gets u a bit bloated and hence the end result? i really don't know what to suggest to you diet wise, you have to figure that out for yourself. I know you said that you changed your diet and it didn't help, but I think diet is the key. Exercising should help as well.
Or may you have IBS? Have you thought of going to the doctor and having a chat? It might be embarrassing, but it won't be half as embarrassing as blowing off like a trooper on the flightdeck!