I just had to post to this message. Our sweet little Rexy is 13 weeks old. He goes "almost" everytime he hits the grass and my husband is home all day and takes him out very frequently, and we have a doggie door so he goes out a lot with the older dogs.
So....... this means that he doesn't have very many accidents in the house - if fact, he may go 2-3 days with no accidents in the house - and we have wood and concrete floors, you can see the pee puddles, so it's not like it's hidden in the carpets. But..... I know full well, if my husband didn't take him out all the time and he didn't go out with the other dogs many many times a day, that he would be pottying in the house.
They just don't quite "get it" at this age - but they will with time, patience, and consistency. Rexy has definitely been easier than Rowdy, but that is due to the doggie door which we did not have till Rowdy was about 5 months old. It made all the difference in the world - but I know that not everyone can have a doggie door!
Don't fret, it WILL get better!