Potty training question! My 3 yr old wears undies during the day and diapers at night. He pees on the potty but doesn't want to poop and will hold it until it literally starts coming out, then he'll sit on the potty and let it go (not a full poop, but enough where he feels better). Anyway, lately he's been holding his poop all day just so he can go in his diaper at night. Any advice or suggestions??