Hi. I know what it's like to go through this, I'm almost 23 and got my first grey/white hairs in the second grade, so about 7-8yrs old, and I have been getting them ever since, but I promise it gets easier to deal with.
The reason for me getting them so young is that I have Cherokee on both sides of my family but it's more prominant(not sure if thats the right word at the moment lol)on my fathers side, and other than my father on his side, they all started getting it in their early to mid teens or later, but my moms side started getting them in their 20s, so if you have any indian blood that could be a definate possiblility of an explanation. As for the solution, I personally dye my hair so that it doesn't show, but you could probably talk to your hair stylist about alternatives to that if you don't want to. I hope this helps, and I'm extremely tired, so I hope it makes sense as well