I need help with getting my almost 5 year old son to poop on the potty.

My son WILL NOT poop on the potty. Not just that, he just WON'T poop. He constantly has poop skid marks in his unders cause hes sticking his hands in his butt to literally push it back in. We've tried timers, we've tried the reward system, we've tried giving a gentle daily lax. Hes gotten so constipated we've had to give him enemas, which to say the least is traumatizing to everyone involved. We've talked to his doctor, who suggested most of these things, but I'm worried because hes supposed to start school THIS FALL and they won't let him if hes basically incontinent not to mention I don't want him getting picked on.He's never been watched by anyone other than myself, my husband, and my parents so I know hes not been abused. I'm just at my wits end and I'm ready to start making it a disciplinary issue but I don't want him more ashamed of this natural function.At this point I'm feeling very helpless and open to anything. Please help. via /r/Parenting https://ift.tt/2ISFPSa