HI and welcome to YT
! You're doing everything right, so try not to worry too much. Your kiddo may not actually have pneumonia, but may have kennel cough or another "cold" -- which in puppies can progress quickly and dangerously to pneumonia - so this is probably why your vet wanted to give clavamox. Did you get he kennel cough vaccine? If yes, he probably got this cold from the vaccine itself. Personally, I only give the core vaccines to my dogs - not the elective ones like kennel cough. It's not one you're required to give, btw.