Another post about poop

Oliver has been having poop issues. He holds the poop in until he's so grouchy and in such pain that it comes out whether he wants it to or not. That's usually every three days or so. In between times he's very grouchy and has no energy. After he finally poops he's the happy little boy we all know and love, but then after a few hours it's back to the grouch who refuses to poop.
We've been giving him laxatives to try and help him. It also has a stool softener so it won't hurt him when he does go. It makes him need to go but he's so strong willed that it still takes three days of grouch to get it out.
He says it's scarey to poop. He said it doesn't hurt, he just doesn't LIKE it. We make a huge deal about the poop when he does it - the song and dance, the treats, the fun activities that are reserved for after poop. Nothing seems to help.