While I am sure this is very alarming for you, chances are it is hereditary and if that is the case, there is not much you can do about it. However, there are other reasons the hair turns grey before the standard age of 35 years old. If you start to lose what is called Melanin pigments, your hair will go grey. 

The main causes for this loss of pigmentation are:  

1. A lack of vitamins, especially vitamin B, copper, and Iron. A deficiency in these nutrients causes what is called pernicious anemia. Supplementing your diet with these vitamins and nutrients can help reverse the problem of going gray early.
2. A time period or life experience of extreme stress or constant anxiety and jealousness can cause you to go gray as can chronic illness and hormone imbalances.
3. Oddly enough, too much sex can cause you to go gray as well. If you are having sex every day, try backing it off to every other day to give your body a chance to recoup and regain its hormonal balance.
4. Using too many styling products or tools to style the hair like hair dryers, curling irons, etc can cause damage to the follicles and roots of the hair, causing them to go gray. It is important to keep your scalp clean and do not wash your hair with water that is too hot.