Another thing -- what kind of conditions did your puppy come from?
Winston, who is now 10yo, and my shih-tzu golden child came from filthy conditions. We went to see puppies from a classified ad and didn't realize until we got to the house that they had many breeds for sale and must be getting them from puppy mills. He was only 6wks old (maybe 8 -- it's been awhile) yet was born in Oklahoma and we live and got him from Virginia...
We went there to get a puppy and you better believe I don't regret getting my best friend even if he came from a puppy mill. We told the people we had come to see shih-tzu's and they brought Winston and two sibblings out. We picked Winston and he was given a bath immediately. We drove straight home, gave him a bath and took him to see his grandparents. He smelled like poop (really really badly).
He was terrible to house break and he would go in his small crate even if left for fairly short periods of time. I started taking him to work with me so he could go out frequently and at night for awhile, he'd sleep in this pet carrier that wasn't a whole lot bigger than him and had a pet mattress that covered the whole bottom. The pet carrier would go on a low dresser on my side of the bed so he would be right by my face basically. He'd ride in that to and from work. One morning as I was leaving, I smelled a terrible smell from the crate and took the mattress out. He had been peeing (I guess at night?) on the mattress and it had gone right through to the bottom (not wet on top) and smelled old and rotten. I think because he had lived all his life in filthy conditions, he didn't think even twice about peeing where he slept.
I remember how hard he was to house break. We had a big improvement when I alone started taking him out and praising him. H would take him out much of the time and would say "good boy" when he went but it sounded like monotone basically. When I would tell him "good boy" it would be all high pitched like his own personal cheerleader. I can remember before he got it, I'd see him walk into the room (we did keep a close eye but he did get to walk around some, too). I'd take one look at his guilt ridden face and know it was time to hunt for it because he'd peed or pooped in the other room and sure enough. I think he thought it was bad to go, not just bad to go inside. He did catch on fairly fast once I started taking him out myseld (and cheering him on) and we let him start sleeping on the bed and slept light so we felt if he moved off his pillow.
Just in case that helps! I really think he'd have been easier if not having come from a dirty place. The other puppies we've raised, including another shih-tzu, have learned way much faster.