What's wrong with my kitten? please help?

2 weeks ago my mom went to the pound to adopt a dog she saw online. I went with her, and she said I could adopt a kitten (no cats, because they'd fight with the 2 we already have). I saw this little black one meowing and playing with a ball in the front of the cage and I instantly fell in love. (: I took him home and he was covered in fleas (the pound we got him from doesn't treat any of the animals, just gives them shelter and food), so I gave him a flea bath, and he seemed to be doing fine. But about a week after we took him home, he started getting very runny eyes, stopped eating as much, and got really lazy. We took him to the vet, and was put on some antibiotics. Acouple days later he started throwing up and having really watery diarrhea, so we took him back to the vet, and his old antibiotics were replaced with a different set. A week later, he STILL has shown no signs of improvement, and hardly eats, or moves. He does drink normally though. I'm 15, so I can't take him to the vet myself, but I'm really worried. It bothers me that he hardly moves, and I hate seeing him so skinny, and that just seems to be getting worse. Does anyone know what could be wrong with him? The vet is closed for 2 more days and I don't want him to die.):