He's a doll! They grow very quickly, don't they. Just means he's a thriving lil boy.
On average he will gain about 3 oz. a week during his major growth time. Up to 6 months, then it will slow down. And of course, that's just an average. It could be a little less, or a little more. But weekly weight gain and growth as a puppy just means he's on the right track.