What Can Cause Hair Loss From The Entire Scalp?

I am loosing my hair from my entire scalp. I have oily and itchy scalp. But there is no fungal infection in my scalp. My scalp sweats much than average. My age is 22 yrs. Wt-105kg. Height- 165 cm. There is no bald head history in my family. I am not taking any kinds of drug. I am an obese person. I have no lethal and contagious disease. How can I prevent my hair fall. Am I gonna bald headed permanently? Plz ans me. I will be highly grateful to you .