Ohhhh, do I know what you are going through!
I adopted a 3 yr. old dog in July, and found out when I got her home she had never really been house broken. There is a long thread about it with the subject 'separation anxiety?' (I think it's still there under dog behavior).
She did the same thing as your pup- I would take her outside when I thought she needed to go, and tell her "go potty". She would not go, then go INSIDE and go potty! A lot of the time I did not get to catch her in the act, which made it even more difficult and frustrating. Everyone here at Pet Talk would tell me to keep her in her crate always when I was gone or could not watch her. I resisted at first because it seemed like it was too long to be in there, and she would also go potty in her crate. What finally worked with her crate was to take the blanket out for shorter periods at times- for some reason then she stoped going in her crate.
As for her going outside, it just took a lot of repetition. I would take her out, and if she did not go within about 4-5 minutes, we went back inside and I would keep her where I could see her. Then maybe 15 minutes or so later, it was back out again. When she finally went outside ON COMMAND, I praised her alot and gave her treats. Still though, I had to do that quite often for awhile. Now, her reward for going outside is a game of ball- she LOVES ball. Use whatever works for your Pup.
It has paid off now, and I don't remember her last accident in the house. In fact, now she does not have to be in her crate unless we are gone for a long time. I am hoping that we can work up to never really having her in her crate, unless absolutely neccessary.
And the bathroom thing: It did not work for me. Just like what everyone has said here, it was too big, and she used one corner to potty in.
Good Luck! It will work out. I know that there was time when I thought it wouldn't, but it did.
Keep us posted on your progress.