Well, Sammy went to the vet yesterday, and at 4 months, he weighs 45 pounds. At two months, he was 20 pounds, so that's quite a bit bigger than yours was, but Sammy was one of a litter of just four, so maybe that's the reason for his large size as a pup? His dad weighs about 110, so I wonder if he'll be around that size too. Right now, at 45 pounds, he is really pretty skinny. He's getting taller, and is starting to not look as much like a puppy anymore. You can feel his ribs and spine pretty easily, and the vet said he's just thin, not underweight, but I may up his food anyway as he is evidently ALWAYS STARVING. You should see him scarf down his food!