Check his skin. If you can pinch the skin together and it stay together he is dehydrated. He needs to go to a vet. I can't think of what it is called off hand, but my puppy had the same thing wrong. They hooked him up with iv's and got some water and nutrients in him. The symptoms are diarrhea, vomitting, and not able to eat. This is really serious...so act soon. Best wishes!!!