Re: mom at her wits end
First of all, I don't know a doctor that diagnoses kids at such a young age for ADHD. Has your child truly been evaluated for this? Diagnoses for ADHD should take months and it does not happen in just one visit.
Another question - are you with your son all day and where are you when he is peeing and pooping? It seems you need to catch him in the act.
When he does this behavior, you have to follow with discipline. I would still make him clean it up, and then take away his favorite toys for the rest of the day. It's all about the discipline!