Our 4.5 year old son has been potty trained since age 3. He still wears a pull up for his nap and at nighttime. He probably poops 50% of the time in his pull up. I'm worried he can't hold his pee overnight (our older child wore a night pull up until he was 5.5), but I'm also ready to stop him pooping in his pull up instead of on the potty. What are your thoughts?