Your very young for this to be going on and I'm sorry you are.
Every one loses hair on a daily basis, this is normal around 100- 200 hairs a day or more. But if hair loss runs in your family you may loose much more. Other factors may be meds taken or diets this will cause more hair loss than normal. This can be heredity from parents either one or both.This is either male or female pattern hair loss causes may be from stress,illness, physical stress,high fevers or heredity.Hair ties, pulling hair, curling irons all can cause some hair loss and damage. With protein and iron intake this may help with more hair growth and protect from any more damage. Thyroid disease will also cause some if not all the reasons you are loosing hair.
This happens over time (not over night) when shedding normal you may not really notice, but if alot is coming out you will this is focal hair loss. Men start to loos hair and show bald spots , women loose hair over entire head, but may also have bald spots.How you treat this depends on the cause!
Hair loss that runs in the family can be treated with medicines or with surgery such as hair transplants. Things to consider--
Which treatment is most likely to work?
How long does it take?
Will it last?
What are side effects and risks?
How much will this cost and does insurance cover this?
If this is inherited your hair wont grow back naturally treatment may help for some to come in , but not much, If medicines stress, or damaged hair is the cause it often will come in again, but need to rid yourself of the cause.