My son was a major withholder. He intentionally would try not to go, then get blocked up. I had to take a two pronged approach with him. First we started giving him Miralax so it would be harder for him to hold it in. Miralax is basically a mild stool softner available at most drug stores. I think the initial dose was 1/4 of the adult serving dissolved in four ounces of liquid. We gave it a few days (this is not a quick fix), then adjusted the dose up or down based on his bowel habits. At the same time, I started working with him to poop in the potty. The reward system was a disaster, but something did work. First, I got out the little potty chair (he was using the big one for peeing), and taught him how to pull down his own pants. Then, I told him if he needed to go poop, all he had to do was take himself, and call me to wipe. He was so embarrassed about having anyone in there with him, this seemed to help. Secondly, he was really into stories at that age, he loved to hear about times when my brother and I got into trouble, etc. So, at bedtime each night I would start telling him a really good story. However, I would stop before I finished it and tell him I would tell him the ending when he pooped. Or I would tell him about this other great story I would tell him when he pooped, and just give him hints about what it was about. After doing those two things, I just quit talking to him about it. Before long, he was going much better. Between the Miralax and potty training, he eventually got lined out. I will warn you that withholding never really goes away. My son still takes a small dose of Miralax each day. He does pretty well most days, but when we are traveling or things are stressful he tends to start doing it again. My doctor assures me this almost always happens, and we are able to recognize the symptoms and get him lined out before things escalate. Good luck, feel free to e-mail if you have any additional questions.