Sorry for the probably TMI post, but if I can't talk to other parents about poop, who can I talk to??

My 3.5yo son has been peeing in the potty for a while, no problems. Poop was a different story. But recently we got him going and we had some great success for a few weeks. He was still reluctant to go and sit on the potty, but he was doing it with less and less whining every day.

Because he was so apprehensive about pooping for a while before and during the beginning of using the potty, we've been giving him Miralax (under Dr. supervision) as well.

Well, suddenly this week he seems to have totally regressed. He's been holding in his poop for a few days but we can see that he's so uncomfortable dancing around. When we suggest the potty he sometimes says he wants to go, but then we get in the room and he freaks out and will not sit on the potty. He doesn't want a diaper either. I think he's just really terrified to poop!

Did you have a kiddo with a similar fear? Any suggestions on how to help him? His poops are soft - I think he's just anticipating that they will hurt. How do we help him understand that pooping doesn't have to hurt and will actually make him feel better!!

TIA!