How To Stop Severe Hair Fall?

i have lost half my hair by using a ceramic hair brush dryer for a year. because I had very thick hair at first it didnt bother me but now I have noticed that I have actually pulled out half of my hair. The new hair growing appear to be falling out once they have reached about 2 inches in length. My blood test ie vitamins level and thyroid test are very good. What can I do to help stimulate new growth.