Does he stay dry at night? If so, then you can try going without diapers. You can buy mattress pads, like the kind people use for doggy training. I think Good Nites has them. Put one down under his sheet. We did that with my daughter around age 3 and she never wet the bed so we ended up not even needing them. Also create a reward system for poop. For my daughter we gave her “poopoo candy.”

Currently potty training my son and dealing with the same issue and he waits til he gets his nap time diaper or poops in his underwear. I try to catch him when he freezes up and starts to push and I quickly carry him to the toilet.

I'm still struggling with my 4 year old. Except I've done underwear and she'll poop in them.... like she doesn't care. She does hold it too. At this point I'm just like she'll do it when she's ready. I'm tired of fighting and tired of forcing it. She's been peeing in the potty since she was 1.5.... just won't poop

We started potty training last month and now my son is fully potty trained. I agree about gettin rid of all the diapers in the house. I always heard their not ready for potty training till they can go all night with a dry diaper. That’s when we started.