Hair fall (age 21 only) Grow new hair.

I am only 21 and I'm facing hair fall problem for past 3 years. Initially I thought it's because of study pressure. Whereas during these 3 years, I've lost 70% of my hair. I had long hair and complacent hair strands used to fall. I decided to cut my hair short but in vain. Hair fall still didn't stop. My diet could be reason for the start of the hair fall but now I've focussed on my diet and I make sure that I intake all necessary eatables. I'm losing my confidence due to this and this is so annoying now. I don't even use harmful hair products like straightener, hair colour or any spa. It's killing me now. Pls help. I'm so find of long hair. I'm looking for a doctor who can help me stop hair fall and then grow new hair. Thanks in advance.