What Causes Excessive Sleep, Headache And Vomiting?

My six year old son has been excessively sleepy since he got home from school, he laid down right away, had no snack and no drink, (VERY unheard of for him). He then woke up feeling overheated, complaining of a headache, and moaning/crying in pain. I went to get some Tylenol for him and when I returned he was heading to throw up in the bathroom. The vomit was bright yellow, and then he laid down again. When I tried to get the Tylenol in him again, just talking about it triggered dry heaves. It was bright yellow again, but then his little body was just heaving.