K.O.
We had a very similar issue with our 3 1/2 year old. Some things we learned: get rid of the pull ups, set aside a time that he is "scheduled" to sit on the potty for 20 minutes every day (have it always be the same time), then maybe try a relaxing activity while he is on the potty like reading him stories or something. If he is pooping in his pants, then try taking things away, like toys and TV watching privliges. Don't give up, don't give the pull ups back, he'll get there. Oh and... if he refuses to go for a week give him some miralax, 1/2 a cap full (mixed in some juice)once a day and within a few days he will go! :)