I am in the same boat with you. My son is now 5 years old and will use the potty every once in awhile. He can change his own pull up, wipe his own butt, and put a new one on, but he will hardly use the potty. I have also tried the underwear thing and he still went in them. I am at my witts end too. With my son the cheerios thing didn't work. The only difference between our kids is mine will go constantly in public, but when we are home he hardly goes. But I am going to talk to my sons pediatrician about this and I advice you to talk to your pediatrician. For the record all kids use the potty when they feel comfortable with it. It is hard though when they get to being almost 4 or 5, because it makes you feel like you are doing something wrong or that people think that you are a bad parent. Don't let all of that bother you.In preschool he will still be able to go if he isn't potty trained as long as he can change himself. At least most preschools are like this.