Colonoscopy screenings are generally not suggested until the age of 40. However, you should definitely discuss your concerns with your doctor if you're having unusual symptoms. It's probably harmless, but unnecessary worry isn't good for anyone. Take care :)
If you have a family history of it you might need to get your colon scoped at a younger age than usual.
You CAN ... But it's not common.
Cancer can genetic also. About 20% of colon cancers are thought to be caused by inherited gene mutations. Consult your doctor for any detail of it.
19 is not a kid any more. Diseases don't care how old you are. Sure, it might be common as you get older, but that doesn't mean it can't get it at a younger age. If you are concerned, go to a doctor and get checked.