I had one that was doing this and it was a fine line between whether he was really ready or not in the sense that he couldn't hold it more than 15 minutes - ie unable to stay dry for an hour which is one of the signs of readiness. He was so afraid to have an accident that he basically lived in the bathroom. He was in underwear. When we switched him back to pullups he relaxed and had the occasional oops but he actually started going longer between trips because he knew it wasn't as big a deal if he did have an oops. Within a month he was going the hour and we moved him back to underwear.