S.N.
I had this exact same problem!! My son did start holding it and had to have stool softeners to help him go. But what worked for me was I went to the dollar tree and bought 10 little gifts and wrapped them I told him everytime he goes potty (poop) he gets a gift. He was so excited to open the next present he wanted to go poo in the potty. It took about 20 presents in all. All a dollar and by that time he was so used to going poo it became routine. That was definitely worth the 20 dollars!! Anyways I hope this helps. Good Luck!!!!