Puppy won't eat

[bvw001]

I recently adopted a puppy from another state, he was driven 7 hours to get here. The first night I had him he was very energetic and ate his food, which is the same food that was given to him at the shelter. I got him saturday at 1 AM. Then Sunday, he wouldn't eat. He also has diarrhea and little energy. He still get excited, but all he wants to do it sleep. I have tried chicken and rice, beef and rice, all kinds of wet and dry foods, and he wants nothing to do with eating. He refuses treats too. I took him to the vet yesterday, he doesn't have parvo or worms. I'm extremely worried.