If he is eligible for Head Start, there's help. They are geared towards children with disabilities and even if the family exceeds the income guidelines you should still apply because they give precedence to kids with disabilities. My daughter was the same way and after a while, she got used to using the toilet in Head Start (they have little ones) because everyone lined up and did it. You know: come inside, hang up your coat, toilet, wash up, get a snack. Eventually they get into that little routine (peer pressure can be a WONDERFUL thing) and they get with the plan. Go see them and apply even if it is mid-year.