4 month old German Shepherd WILL NOT potty train

Question
Hey, I've been reading through some of your answers, and I thought I should ask you for advice on this matter. Ok, I adopted an 8 week old puppy from the local animal shelter, and he is 4 months now, and he still wont use the bathroom outside. I have tried crate training, I've tried the puppy pads, I've tried putting his own poop outside where he needs to go, but to no avail! He's on a schedule, and I take him out no more than 20 mins after he eats/drinks, when he wakes up, before bed, and in between whenever he acts like he needs to go. I had him out for almost 2 hours one time, and he DID NOT go, but the second we walked through the door, he sprawled out and wizzed in the floor! He's an over-all excellent puppy, very smart, and obedient! He's doing excellent with commands, and is very attentive for a puppy. I just had him neutered last Thursday. He's healthy, no bladder/bowel problems whatsoever. It's almost like he just doesnt like anywhere else but the carpet! HELP if you can!!

Answer
When you are around you need to keep a close eye on the dog.  Use closed doors or gates to keep it in the same room as you are, and perhaps as I do, a short chain fastened to the computer desk.  If you catch it in the act, give it a sharp ''Ah, ah, ah!'' and take it out.  When you can't watch it, crate it.

Perhaps over the holiday, you will have some extra time.  When you take him out, walk, walk, walk.  Keep moving at a brisk pace unless he stops to sniff.  Give him access to popular places such as trees and fire plugs.  He can only hold it and walk so long.  When he finally has to go, lavish praise on him.