S.A.
When my son was going through potty training the first couple of times he went poop in the toilet with no problem. However, after a few times, he just didn't want to do it anymore and wanted to use a diaper - only when he needed to poop. We really tried other methods like sitting with him and talking, holding his hand, rubbing his tummy, etc. to help him through the process. Yet, he would just say he couldn't and could he have a pull-up. Rather than have him sit on the toilet for so long (which is not good) or have him hold it in, we put the pull-up on and let him do his business. Then I showed him all the pull-ups and told him that this was all we had. When he was done with the pile of pull-ups we had, then he was going to have to use the big boy toilet. This seemed to work for us (also, we continued to use a "potty chart" where he put stickers up every time he went in the toilet and at the end of the week he got to choose some kind of small toy or book).Good luck!