Loss of bladder control is what my/my mom's dog GiGi had for about a year before she passed away. It just kept getting worse. The vet I think called it Kidney Failure. But GiGi was 16 years old and a dauxie. I'm sorry to hear this is happening to your Yorkie.
It's so very sad when we see them going down hill and can't do much about it.
Wish the life span of dogs was much more than what it is. Sending you a big hug, cause I know what you will be going thru.
Take Care.....