You said that your child started having problems at age 3 1/2 which is pretty young for a child to hold bowel movements (e.g. from fear of painful BM's) resulting in backed up stool. I have read about a lack of nerves in a small section of the intestine that can cause chronic backing up of stool in younger kids. It is called something like "Hirchsprung's Disease" but I'm not sure of the spelling. You might ask your doctor about this. Good luck.