I need some advice

My almost 4 month old son has been fussier than usual and is wanting to eat (he's breastfed only) a lot but only to spit up. I'm talking enough spit up to probably be the whole meal he just ate. I'm only feeding about every 3-4 hours and I don't know exactly how much. But could he be sick or have a little stomach bug or something !? This is crazy, he's never been like this before.. He's also only wanting to fall asleep while nursing 😔😳😢  he's in his 3rd outfit in the last 3 hours 😫