J.L.
I say stop stressing over it. It's not going to help the situation. When my son was 3 1/2, I took away the diapers and gave him undies and pull-ups. I told him he could choose which to wear, and he was in charge of changing himself. After a few days in pull-ups, he discovered undies were easier and faster. He knew how to use the potty, but the diapers were easier for him.