Best to just go by trial and error, everyone has little food sensitivities, most people don't realize it. Try eating a little longer before you train, maybe a bit smaller portions if you feel to have overeaten. Also, make sure you are well hydrated before you eat, at every meal. Washing food down with water dillutes your stomach acids hence food isn't digested as well. Also try adding some green veggies to every meal, especially in the place of other carbs which will spike your insulin. Nobody want's to do it, but if you start replacing grains and refined carbs with raw vegetables saving for post workout it makes a big difference. If it's an ongoing thing, look into getting some good digestive enzymes or probiotics.