Denise, I'm by far NOT an expert! I have a yorkie boy, too, (my first!) and he's now 6 months old and just now seems to 'get it'. Believe me...this ISN'T an exact science so don't beat yourself up over this!!
Topher did pretty good from the get go on the pee pads, but it didn't seem to 'sink in' until the last month or so. I am a HUGE believer on the treats and praise, too, and Topher loves getting both when he does the right thing. He still made mistakes and peed elsewhere from time to time, but we kept him VERY restricted as to where he could go in the rest of the house. (we kept the kitchen blocked off...we have vinyl flooring in there and it's easy to clean!) I think that's key to save yourself from going crazy and having him pee where he isn't supposed to. Parker is still only a little guy and the praise and positive reinforcement WILL work eventually if you're consistent.
Also, I've found that Topher did/does better if I have two or three pee pads out and I always leave them in the same areas in the kitchen.
The most IMPORTANT thing I think I've learned, though, is that you have to keep your eye on them AT ALL TIMES...it's difficult, but it saves finding those pee spots later on. If you know where he is and what he's doing, you won't find surprises later and get wet feet!!
I don't know alot about 'marking' 'cause I haven't experienced that with Topher (yet). I'm sure there's more seasoned yorkie owners on here who could help you with that.
I just wanted to tell you not to stress too much, hon. Just keep him confined to an area where it's easy to clean up piddles; take him outside after naps and eating; keep up with the praise and treats and don't take your eyes off him for a second!
Don't beat yourself up! The 'lightbulb' will go on over Parker's head soon. I truly believe that pups are like children...they each learn at their own pace, some sooner than others, but eventually, if we're consistent and watchful, they'll learn what we're trying to teach.
Take care and don't stress too much!