I have a healthy diet and exercise regularly but cannot pass a stool naturally. i have tried a colonic and tried different things. what could this be?

Fiber: You have a slow transit time - have your thyroid checked. The more likely cause, though, is inadequate fiber in your diet. Here's an easy fix: eat at least one meal a day of high fiber cereal - not cornflakes or wheat flakes which are 1-2 grams of fiber per cup but cereals that are 10-12 grams per 1/2 cup: (in the usa, they're sold as fiberone or allbran.) try to eat 20-40 grams daily for relief.