Greying hair at 17?

Hey Im a 17 year old guy and my hair has been going gray for the past year or so but its picked up alot recently. My grows fast, but I have sections where its like my natural color just stopped and its growing in gray in those spots, like really prominent roots from a dramatic dye job or something. My parents are almost 50 and barely have any gray hairs so whats the deal?

maybe its stress. Ask your doctor about it. it may be a health problem.