3 year old son sick vomited once slight fever what could it be?

At about 3-4 in the morning the other night my son woke up coughing i got him back to bed and then he woke up that morning and seemed fine then he didnt want to eat didnt want to play and said he was tired this wa around 11 am. then he came inside and fell asleep woke up and seemed a bit better stikk tired and felt a little warm.. i took his temperature from under his arm and it read about 37.7 he said he felt a lump in his throat but that was it he didnt say his tummy felt yucky or anything when i asked then randomlyhe sat up and threw up about two three times and then wanted to play again. played for a bit then he took another 2-3 hour nap. woke up ate some toast and didnt throw up his fever came and went. this morning he woke up and pooped in his pull up but said he was too scared to get up. i dont know if heis making up storied or if it came out without him knowing. anyway it doesnt sound like the stomach flu to me but what could it be? he hasnt had anything different food wise.. the only thing i couldthink of is the day or the night where he woke up coughing me and my friend sanded down old paint off bunk beds and he was pretty much beside us the whole time.. any ideas???