Are you crate training?
We got Porter at 8wks. He was fully house trained in a month and a half. We crate trained like CRAZY!!!!
Do you know to take the dog out RIGHT after eating, playing or drinking water? We would take Porter out to the same place in the yard each time and keep him there until he did his business. During the day he was in his crate and when we took him out we took him directly outside. When he did begin to go in the house (we were nearby most of the time) we sternly said NO, and immediately took him outside (and sometimes he just kept right on peeing! :p ), but it worked!! I don't think we did anything special, maybe we just got lucky! Good Luck to you!
Oh, we also tried to limit his play area...near his crate and we tried to keep him in the same room as the crate. We stayed with him and played with him, then took him to pee, then inside again but to a different part of the house, then to pee, and so on...
I don't know if that had anything to do with the quick training, but I think it helped him to realize that the crate was not his only 'den'. Any behaviorlists have any thoughts on this?