I just posted this in another thread but here it is again...
I wish I could help, but I don't have my Yorkie yet

I do have an English bulldog, who just turned 6. He did start peeing in the house - right in front of us sometimes - just last fall. I took him to the vet, because I figured it must have been physical. He was 100% trained when we got him at 14 weeks and has NEVER had an accident in the house (for over 5 years) And we had nothing new, no changes that I thought could prompt a "mental" reason. But the vet checked him out and said he is fine, nothing wrong. It lasted for about a month, he had a accident about once every 2 days. Then I took him to a trainer in town here she said he FORGOT his training

I thought the whole thing was crazy, but, I did what she told me and I got a whole "plan" in place to re-house-train my 5.5 year old dog

Anyway, he stoped having accidents. So who knows? I still don't! Maybe it was physical and he "got over it" or maybe it was mental and he "got over it", all I care is that _he got over it_

So best of luck, hopefully your baby gets over it!