How much should I feed my puppy?

Generally I feed what it says on the bag..to keep from over feeding. Are you sure that's what the bag says for his age on the bag? A dog will always be hungry...unless they are sick...especially larger breeds. You should be able to tell by his physique if he is fine. You should be able to feel the ribs, but not physically see the ribs. He should have a defined waist. There should be no excess fat around the tail area. You should be able to clearly define his chest, body cavity, waist. He should have visible muscle definition. If your still unsure call your vet. He could just be a growing boy or he could just be a porky boy.