Sounds like you've tried everything. I honestly think that no matter what you do, there are always some dogs that will never be 100% potty trained. I thought Lacy was 99.999% until I went back to school...now she's started pottying in my roommate's room occasionally

I even had her treated for a urinary tract infection.
Have you thought about ripping up your carpet and having hard floors? When I have my own house one day I plan to have all hard floors (I know some people like carpet too much though).
I know it can be frustrating
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~Magnifique Yorkies~
Purchasing from backyard breeders, pet shops, and puppymills perpetuates the suffering of other dogs.
Educate yourself and buy from reputable breeders or rescue.