My stool is always thick heavy pasty but soft but it's still hard to pass. what can i do to get my stool to become more light and loose?

Roughage: Eat foods high in fiber, more greens, oats, bran etc. Also metamucil is a great source of roughage. It contains psyllium, which should solve the problem.

Fiber, fluids & exer: I don't know about making your stool "more light" but you can't argue against fiber, fluid & exercise to keep from being constipated. Ideally, you'd get your fiber from your foods but there are also fiber supplements available along w/stool softeners, too. Don't worry about consistency as long as you don't have to strain. Check w/your doc re need for colonoscopy (low risk vs high).