I wish my book had the answers to how to overcome shy bowel, but alas it doesn't. I sometimes hope that someone, somewhere will come up with a remedy, and let all us shy bowel sufferers know about it.
Bob Marley said, "a hungry man is an angry man". Well so is a man who needs a poo but can't have one.
In Shy Bowel sufferers, there's something odd going on in the brain/nervous system, that's for sure. Although in a pre industrial time maybe it wouldn't have been such a problem. But living in this modern world, the shy bowel brain is definitely not serving us well.