Hi Welcome to YT!!
Your baby is only 12 weeks old, He is NOT going to be fully potty trained until he is atleast 6 to 12 months old...it takes months to train them.
I have a 20 week old pup in training...when I got him at 12 weeks what I did is I look at him while he was in his play yard and I said need to go outside go potty and I let him out and went right to the door and I said "need to potty" and I opened the door and took him out...the whole time I'm saying "go potty" until he does than I throw a potty party
and give him a treat...than we go back in and I let him play for a few minutes than I took him back outside to potty again before putting him back in his play yard...I never give him full run of the house you have to confine them to 1 room and I never take my eyes off of him when he is out of his play yard...He is 5 mos now and doesn't need to be in his play yard as much cause he lets me know now, he has to potty and can go longer in between potty breaks.
I took him outside to potty every 1 1/2 to 2 hours when he was just 12 weeks old now I'm up to every 4 to 5 hours, I take him out after he eats, after playing really hard before putting him back in his play yard...If I do catch him in the act I just walked over picked him up and said NO to him in a firm voice and quickly take him outside and say "go potty" than its back in to the play yard..no more play time.
Maybe you clapping your hands and yelling no is scaring your baby, that why he is running under the sofa...try just saying no to him and take him right outside and than put him in his play yard or crate until time to go back out....You have to set them up for success and not give them a chance to fail...You have to be consistent and very patient with them, it takes months to get a Yorkie fully house trained...They will pick it up it just takes time.
There is a thread that one of the members opened its called " the Joys and the Frustrations of a puppy....I will find the link and post it for you so you can join in and get and give great advice
