My 6 year old has been struggling with encopresis for over a year. We finally saw a specialist, a Pediatric Gastroenterology who gave us a lot better advice then his regular Ped Doc. She said his bowls were very blocked and the softer stool was seeping out around the hard large stool. He had bad tears in his anus. Previously I didn't know any of this. We finally found his currency to get him to go even if it hurt: Video game time with dad each day. We tried sticker charts, rewards of every kind, time outs for pooping his pants (punishment is a big mistake by the way. I still feel very guilty about that and think it made things worse for him.) He is finally going almost daily, which is HUGE!! He still doesn't want to, but it seems to be getting better every day.
The doc suggestions were as follows: Miralax (she says it works the best by far for kids) Ask him to sit on the toilet for 5 to 10 min (no longer then that) everyday at about the same time, and at first twice aday. (For us we do right after school at 11:30 and again around dinner time. And even though I felt she might not think our reward of video game time was a good one, she did! Pretty much use whatever you have too to get him on a health reg schedule. It takes a LONG time to fix this problem so consistency is key. I the past he would start to do well and then we would forget to reinforce the behavior and the withholding would start again. You may have to do this for months. It doesn't sound like your son's problem as progressed as far as ours, so it's better to fix it now. It caused us all a great deal of stress which I am sure made things worse for our son. This is a way more common problem then I ever knew. Kids much older then ours have it, so try not to let it guilt you (I felt very guilty in the beginning, Like It was my fault, and that just isn't true) Good luck and keep your head up. It will get better with consistency.
A.