Hey guys i am 19 and have a lotta grey hair. Help required urgently.?

The bane of the whole thing is that most of the grey hair is towards the front. I am quite thin but my immunity is very strong. What can be the causes? Is there any way that i can turn grey hair to black again (not by dyeing). I read on the internet that even masturbation can be the cause. Help, coz i am in a dilemma. Suggest me the cures and the time period they shall take for effective results.I shall be greatly indebted.