I Am 18 Years Old Female Suffering From Extreme Hairloss

I am 18 years old female suffering from extreme hairloss since 3years and now my hair has become very thin and the new hairs which are growing are very fine and thin. My pcod and thyroid tests are normal and ferritin is 16.93 ng/ml for which i am taking ferrium xt and biotee plus tabs since a week but still can not see any reduction in hairloss and my periods are always late but not so heavy. What can be the reason for my hairfall.