There are many, MANY other things that can cause chronic constipation- I know because I have it. I also have hypothyroidism - which can cause chronic constipation and MS symptoms if you need an increase in your dose of medicine, as well as fatigue, depression, thin hair and nails, abnormal sensations throughout your extremities (numbness and tingling which can be confused with MS).
If you're very concerned, I would go see an MD and asked to get your thyroid hormones checked.
Try this - When my gallbladder was acting up, my doctor wanted me to get an ultrasound after an attack to see if there were any stones in there. (there were), but while I was waiting for the results to come back from the ultrasound, he had me on a strict fruits and vegetables diet only. As well as only water. And chronic constipation no more! So try it for 3 or 4 days. Eat only fruits and vegetables (Believe me, you'll be eating all. the. time, because you'll be super hungry) and see if it changes your stools. And again, if it doesn't - get your thyroid checked. It could be as simple as that - ESPECIALLY if you just had a colonoscopy 4 years ago - at your age, with a clean colonoscopy 4 years ago, your changes of colon cancer are nil.