My dog is sick. What does he have?

Could be parvo.
You need to get him to a doctor asap.
If you have a 24/7 vet nearby, you should go.

Parvo is a serious doggie illness that cannot be cured without antibiotics.

EEny, meeny, chili beanie, looking in my crystal ball.
Take the dog to a vet, how are we supposed to know what's wrong with it.

Any time a dog is feeling ill for more than a day - it's time to see the vet. The symptoms you describe can be representative of a whole host of illnesses and diseases. Even your vet won't be able to tell you from the symptoms you describe what's making your dog ill until he runs some tests. So, get your dog to the vet NOW - that's where he needs to be.