satyamshrivastava,
Most of the time, a person's height is determined by genetics. However, there are a few medical disorders in which too much human growth hormone is produced and the patient is much taller than anyone in his family or very tall for his age.
So, you should have a thorough examination by a physician to make sure you do not have a hormonal imbalance. But, if this is just the way you are, then you will have to make the most of it.
Good luck.