He's 14 weeks.
He's very thin. I feel abnormally thin.
He is wormed regularly and all my dogs get Revolution once a month. His poo is normal.
Maybe I'm just over anxious. He's the size of some of the 4 month old pups at training.
Sounds within tolerance....GSDs take many months to fill out....many.
I'd much rather have a leaner pup while their skeletal structure is forming and maturing than an overweight pup....for that matter..for their entire life.
Perhaps, your dog is growing so fast in other dimensions and areas the "thinness" is the last to be effected.
As you stated...."he's growing like a weed"....