vinegar will work...I am so sorry and I don't mean to be rude, but I really think you might want to find that baby a new home, it sounds as if your not very happy with him, and they pick up on your moods...He is only 5 months, we don't let puppies go till they are 12weeks old which means, 3 months or sometimes longer, if you expected him to be trained by 5 months you haven't been reading alot on yorkies, they are the hardest to train, and too he doesn't know you, scared to death, and God only knows of the situation he was in at the breeders...
Please sell him and find him another home...