L.G.
Both conditions are related. You need to get him to the doctor with some backup information so it isn't ignored. Stomach troubles can come from breathing problems and the other way around as well.
Document what happens. He's cooled out with milk so maybe that is something to give him 15 minutes after he's eaten. Is it dinner or any meal. Does it also happen after breakfast. Keep track of what he's eaten before he complains.