My son is almost 4 1/2 & he is diagnosed w/ mild PDD & ADHD. He is still not toilet trained & I am having a really hard time getting him to go. He knows what to do, but just doesn't want to do it. It's like having a wrestling match everytime it's time for him to use the potty! Don't know if it's a laziness thing or what, he just has no desire to get up from what he's doing to go use the bathroom? He is wearing the largest size of pull ups & there getting very tight on him, so I really need advice.