Does he go potty outside at all when he's outside?
When I first got Buddy, I kept him on a leash (inside my fenced in yard) just because I didn't want him to jump the fence. I would take him outside and stand with him for an hour and he's pee, but he would never poop. We would come inside (after standing in the snow for an hour) and poop on the floor RIGHTAWAY

Then the first day I let him run free in the yard, he poop!!!! It was because I had him tied up (on a leash) that he wouldn't poop. It's been about 10 months that I've had him, and he still will not poop when he's on a leash. And he's never pottied in the house since!

That's why I ask if your pups tied up or running loose when he's outside.

BTW - Welcome!!!