Is he on the same food as the breeder gave him? Food changes can upset tummies. And I wouldn't have thought of this, but when my son and daughter in law got their puppy, he had a little bit of a tummy issue and the breeder recommended bottled water for a little while and that did the trick. Even though their water was fine, just the change could cause an upset.
I agree with everyone--a vet visit is in order.
Snoopy bonded with Daddy right away, not so much with me. I stopped making eye contact and picking him up a lot until he was more used to me. (He still loves Daddy best; that's why we got Sally!
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