my son is 3. he is potty trained but im having a problem with gettin him to wipe his bottom after he goes number 2. he will not do it. he tells me no u do it and he will start gagging he has a weak stomach when it comes to things like that. i told him he needs to learn cuz he'll be starting preschool soon. he told me well the teacher can do it than. how can i get him to do it himself? PLEASE HELP!