Just let me say, you have come to the right place. I have a 4 1/2 year old son, that I was having similar problems with. I came to mamasource and got the best advice. he now does it all. We were peeing just fine, with an occasional accident, but he would not poop on the potty at all. We would sit and wait, but nothing. We tried rewards, reading, sitting several times during the day, but nothing, and school was just weeks away. He also did not go to day care, and everyone said that would have helped. Read all the advice you can on this website, but the best advice that I got was to find out what time(s) he was going and try to sit him there at that time. He was very irregular. So, I was noticing he finally started going in the am, before we woke up. Well we would set the alarm clock, and get up an hour before usual, and sit then. He finally started going. We just had to go on his schedule, or before it. He only had one accident, and he was sick then. I hope this helps. I was at my wits end and the mothers here were so helpful. Best of luck. T.
P.S. Try putting him in underwear. When he was out of the pull ups it was a whole different story.