Potty training help

My little guy has been peeing on the potty like a champ for a little while. He goes all day no accidents, however he will not poop on the potty, he will try and then when it seems he is ready to go, he cries and hops off the potty. He asks for a diaper/pull up. I tried holding my ground a few weeks back and not giving in. But he just went backwards and had soo many accidents with bith peeing and pooping. We used a toy reward for going pee on the potty and have one for pooping in the potty as well. Im at a loss for what else to do?