[cherry14]

I literally had almost the same thing happen to me a few weeks ago.

First, I'd take him to the vet IMMEDIATELY.

If he's cleared of anything serious, go to the pet store and get some Nutrical. Give him a pea sized drop 2-3 times a day. Get some Royal Canine Puppy Mousse. It's a canned food. You may have to hand feed him. I had to hand feed my Cherry for a while. I also used a syringe to get some water in her.
I am not sure, but I believe you should NOT be giving him cow's milk. Get some goat's milk or puppy formula from the pet store. I mixed warm goat's milk with Royal Canine Starter kibble to soften it and the starter mousse and fed her with a syringe or with my fingers. These little ones need to eat small amounts every couple hours. He needs to be watched 24/7 for a while. How much does he weigh?

Most importantly, it sounds like he needs to go back to the vet immediately.