Whats wrong with my cat?

Could be an inner ear infection. Is he using the cat box? Male cats can get "plugged" and the backed up urine in their system causes a toxic reaction. keep him calm and comfortable tonight, don't force him to drink or eat if he doesn't want to. Keep an eye on his litter box use so you can tell the Vet if kitty has gone to the bathroom or not, come morning. Good luck dear. You are fortunate that kitty is young and can fight off illness better than an older cat.