My san had/has this- withholding. I would absolutely talk with your doctor about it... even a visit to a pediatric gastroenterologist is notr out of the question (they see tjis a lot). We have been on long-term Miralax and for what its worth, I have gotten assurances from 3 specialists that it is ok. It has worked wonders for us. It takes a little time to get the dosage right... You will need to play with it for a few weeks, so it takes a little patience.
I want to say I totally relate to the emotional side... It is difficlut because it *seems* like just a stobbonness ("Just GO already!"), but the reality is that they *can't* for physical and emotional reasons. And I must remind myself of this OFTEN. Don't beat youself up...
. Everything in your life being covered in poo can really take it out of a person!
I have also found that once things get "going", rewards/treats work. I felt terrible over this and confessed to the pediatric gastroenterologist. He laughed and said "Great!" and talked about how the whole thing can be very pavlovian- "Pooing in the potty is bad because it huts/is scary/whatever" is turned into "Pooing in the potty gets GOOD things and maybe isn't so bad". I certainly wouldn't do it with a kid who didn't have issues, and we definately don't rely on rewards excessively in our house, but with this, it really helped take a negative and give him a bit of incentive and postive feelings about it all. Once it became "regular" we phased out the treats.
I also don't mean to be a downer, but these types of poop issues have a very high "relapse" rate, so don't get discouraged if you find yourself revisiting this. The relapses are much, much quicker in getting back on track. But many kids don't fully get over it until about 7 or 8 or so when logic and the ability to see the big picture overrides the other aspects in this.