Ricky sounds a lot like Teddy. He was originally 100% outdoor trained by his breeder and then I trained him to use pads too. He was so shy about pooping, and even outdoors on a leash, he was upset that he couldn't go do it in private.
For the pads, he would always do it when no one was looking.
The only advice I can offer is to keep up the praise, for pad and outdoors. We throw parties here and give kibble treats. I take care of the pads right away and Teddy happily walks by my to take care of them. It took a long time, but the constant reassurance finally had good results.
Max has zero inhibition, so Teddy was a huge change for me.
