We fostered Bentley (in my album of fosters) that was surrendered to the rescue because he "couldn't" be potty trained.
After a couple of days he was using pee pads fine, but we were still having trouble getting him to potty at all outside, actually he wouldn't even get on the grass.
I spoke with the surrendering owner and she stated that she didn't know if he had ever been on grass before. Just in her house and on the driveway, he was TWO YEARS OLD!
WHAT?!?!?
Never on grass?!?!?!?!?!
We finally started taking him out to the back of the yard (my wife on the patio) and calling him to her. I would stay with him and reassure him and then he would bolt to her.
After a few days, we started throwing his toy into the yard he and he would go after it on his own.
Yay Bent-burger (my nickname for him.)
After about a week and a half...you would never know that the little guy was "scared" of grass.
His forever home takes him on two good walks a day of 30-45 minutes. She said that she has to basically drag him in because he loves being outdoors so much IN THE GRASS!
The biggest issues always seem to be impatience on the owner's part. I mean, does a child go potty the minute you sit them on the toddie? No. Most of scared of it until you acclamate them to it.
Patience, Persistance, and Praise. The three P's that folks need to remember when training a dog (especially a Yorkie) to do anything.
Hopefully some of what we did to help Bentley will help you! 7 weeks is still WAY young, but while IN the house, the xpen with a pee pad should do the trick, just make sure you don't "pee pad" the whole area! Keep it separate from the bed and water!