I have a sick Yorkie and need some advice...?

You biggest concern is to keep such a tiny animal from becoming dehydrated. To stop the diarrhea, feed him some canned pumpkin...plain pumpkin. NOT pie filling. Most dogs love it and it should help settle the gut. Equal parts of plain boiled rice, cottage cheese and boiled chicken or cooked ground beef are good, too ( our vet's recipe). Try giving a little Pedialyte or Gatorade for hydration and don't be too concerned, if he doesn't eat much. He's tiny and has had an ! Good luck!