i personally think it is a phase. My DS3 did this.. he trained himself yet a few months later was weeing and pooing all the time.. I was being driven insane especially as we had a new baby too..

I just said to him.. If you continue to wee and poo in your pants I will put a nappy on you. I also got him to help clean up the mess he made.. He stopped after a few weeks.. but it was so frustrating..