My son was almost 4 by the time he was going poop on the potty full time. Before that he would hide and me and my husband would catch him with his knees up to his stomache face red as a beet and saying "I not poopin', I just sittin'. When he would poop in his pants as I am sure you can imagine it was very frustrating for us and we would get angry at times, not at him, at the fact that we had no idea what to do. We just kept it to ourselves and talked about what to do. One day my husband went into the bathroom with him and found out he had already gone. My hubby handed my son the underwear and told him that if wanted to keep pooping in his pants then he could clean it out. He showed him how to dump it in the potty and then brought it to the sink put a squirt of soap on them and showed him how to scrub them together to get the stain out. My son does not like anything dirty on his hands and after a few episodes of this would go running to the bathroom to make sure he made it so he didn't have to touch the poop. I wish you the best of luck, he will come around and you will both be much happier.
Has anyone else noticed the words we say for the kids such as poop and potty and then end up using them when there are no kids around!! I just think it is funny what being a mom can do for you.