Hello everyone. I recently adopted a 4 week old kitten from a local shelter. He ate some Science Diet kitten food the first day he was here, but today he's been throwing it up shortly after he eats. He's also sleeping alot. He really just wants to sit in my lap and sleep. He does play a little bit and seems very curious about his surroundings. Today I went and bought some kitten formula and got him to eat just a very small amount of that. He's been having diarrhea today as well, and I have no clue what to do. I took him straight to my vet from the shelter, and he's negative for everything and has had some vaccinations since he was at a shelter. My vet said he looked fine on Thursday. Am I overreacting? He was so terrified when I first brought him home, hissing and spitting at me, but now he's the sweetest little cuddly baby! Any and all advice welcomed!