How old is he, and how much does he weigh? If he's very young and/or tiny, get him to the vet NOW! We almost lost our baby Luna to hypoglycemia, if I'd waited any longer she would have been gone
If he's not eating, I posted a formula on the Health and Diet forum here
http://www.yorkietalk.com/forums/showthread.php?t=58036 Please see if you can get him to eat this, or if he won't eat, force feed him with a syringe. Him playing is a good sign,but he can go down fast. When they don't eat, it's best to keep them quiet so they're not burning calories that they can't afford.
I hope he's okay!
