It sounds like you're having digestion problems. The most problematic of the foods you mention generally are first, the milk, second, the sugar, and third the coffee. But it's hard to say since diet is very complicated, and you don't say how soon after eating you laid down. Chamomile is a good stomach relaxant and anti-inflammatory, perhaps try some of that instead of the coffee, milk, and sugar and see how you do, assuming you don't need the coffee to stay awake.