Hairfall, started losing front hair.

Myself 22M. I am suffering from hairfall, dandruff and layers of white powder on scalp.very itchy on the head. I used to head bath for every 2 days.I am losing my front hair slowly day by day. Using Coal tar and salicylic acid scalp solution ,Dankare plus scalp solution for the past 3 months suggested by a dermatologist. But not working. I am losing more hair after using this. A layer of white powder like thing on my scalp. I am trying to remove this  by regular head bath .But it comes back again just after one day again. When I head bath, lot's of hair falling due to this. When i rub comb on my scalp, dandruff like thing coming up including hairfall. I am suffering from this past 4 years. I even cut my hair short due to hairfall, but not working. Not using any oil on hair from the past 3 years due to this.Please suggest me what to do to get my front hair back and to stop further hairfall.