Goodness gracious, people...Some yorkies are bigger than others. That doesn't mean he's grossly obese! My yorkie is 11 lbs
PeanutsMommi, if you can feel his ribs and all the bones in his body and they stick out, then he's definitely not eating enough. If you can't feel the ribs, then he's eating too much.
Just read your bag of dog food and see how much a pup at his age and his weight should be eating and make sure he's at least eating that amount. Let your dog's appearance, health, appetite, and size be your guide on how much to feed