Potty training issues around pooping

My son (3 next week) has been working on potty training the last 6 months. It started out horribly and we couldn't find a good strategy to get him on the potty reliably. I had read every book, tried everything suggested, and not much worked. I decided he just wasn't ready, and gave up on trying for a couple months. His preschool teacher suggested just doing away with diapers completely, underwear only, all the time. This surprisingly has done wonders, and he learned pretty quickly (within a week) that he doesn't like being wet without a diaper. I somehow had never thought of that as a strategy before! He's been completely potty trained with pee for the past month, and doesn't even need reminders.The issue we're having is with pooping. He will NOT go poop on the potty. The process looks something like this... He begins crying, saying his tummy hurts, and crossing his legs. I'll try to have him sit on the toilet, which he absolutely refuses and hates in this moment. This will result in him doing this several times/day, sometimes for days at a time with no BM. When it finally does occur, it's a huge blowout usually in his underwear. My thought is that he doesn't like the sensation of pooping on the toilet for whatever reason. He has never had any issues with constipation. I'm concerned though that now by holding it in for days at a time, constipation may also be a factor for not wanting to go. He's been eating lots more fiber rich foods, and I'm limiting constipating foods (like cheese which he would gladly eat several sticks of before). I've even gotten desperate enough to put a diaper on him for pooping, but by now he hates diapers and wants nothing to do with it. I've tried distracting him while he sits on the toilet, such as with a book or show on the iPad. This doesn't work. Even bribing for a piece of candy, but when he needs to go and is crying, he's not interested in anything.Has anyone else had issues with their child not wanting to poop since potty training? What helps?Thanks for the input! via /r/Parenting http://ift.tt/2tJ9maL