Flaky Dandruff and dry hair. Wrong!

When i scratch my head, such scales/flakes of dandruff peels off from my scalp and inner skin gets exposed. Once the flakes are peeled , scalp feels soft and exposed as if i peeled a wound. This flakes of dandruff condition were present since years and isn't getting better. These flakes are present on the entire left half of head and in the middle of head. Whenever i comb or scratch my head, these peels off. My hair  and scalp are extremely dry and i am facing extreme hairfall and hair thinning.   P s: i am not on any medications and i dont have any medical or hormonal conditions, periods are also regular, no pcos, pcod, or any such medical conditions, i am a non vegetarian and tries  to drink 2 litres of water every day, I am overweight(75kg- age 24, height-5'5in, student at home, distance education)  and not on any workout routine or diet, sleeps 8-9 hours, eats only home cooked food, no junk food intakes, oils hair before bath using cold pressed coconut oil. so,IDK  what's wrong