It's not TOTALLY unheard of to bald that young (I started around 15-16). Look at your family history: brothers, uncles, dad, grandparents, as far as you can go and that can give you an idea of how early u may bald.
If you have any underlying scalp issues get them sorted with good shampoos like nizoral and tgel (imo scalp issues can make hair loss worse). See a derm that specializes in male pattern hair loss and see what they can tell u. It's not the end and of the world. There are treatments that can stop or halt your hair loss. Try your best not to worry about it a lot. Good luck