Does he EVER go outside? Dogs have to be outdoors every single day. Not just a short jaunt, either. Dogs of every size and breed, need strenuous exercise and outdoor time daily. Dogs are not instinctively, by nature...supposed to go on an artificial pad. They are animals, they are supposed to go outside. They WANT and NEED to go outside. You are doing your pet an incredible disservice.
I guarantee you, that your dog is extremely unhappy. It is tired of looking at walls, tired of not being able to do, what it should instinctively be able to. He is trying to tell you something. I don't have suggestions on the piddle pad thing, because he should NOT have to go on one. Take the dog outside!! Let him walk around, sniff some things, do his business. If you can't do that, you shouldn't have a dog. Sorry. That's part of the deal. This is not a DOG issue. It's an OWNER issue.