Id get rid of the puppy pads and take him outside like you have been doing but dont go back in until he goes. Then lots of praise or a treat. Keep at it, he'll get there! :-)
I would put the puppy pad outside and take him to it. This worked well when we moved paper outside with our lab. now is the ideal time too as you can leave the door open for him to go out and you can praise him when he does. When he has the hang of it you can teach him to bark so you can open the door. Our lab always goes in the same spot in the yard where we put the paper so choose a convenient spot to put the puppy pad not just outside the door.
when we got our puppy we didnt put down paper or anything like that, instead every time he went on the floor, we just said "No" and took him outside. we wouldnt let him in until he had gone properly outside, might seem a little mean when they start crying to be let in, but after only a week our pup would try to make it to the back door (if he could bless him) and sit at the back door and go straight outside.
I am having the same prob with my Yorky, I stand outside with her and she runs in and pees on the carpet then comes back out to me. I make sure the door is shut now