I m 16 and I love someone. He propose me on 14.feb.2012 but now he say that he love other girl.?

Nothing...you are very young and love is infatuation. If he truly loves you time will tell and for now move on. It might not feel this way now but trust me there will be many more loves before you get married.

U don't need to quit d relationship,let him know how much u love him.And make correction any where u made a mistake.