What Should I Do For The Hair Fall And Dandruff Forming In Clusters And Is Not Responding To Any Kind Of Treatment?

Hello! I ve been suffering from hair fall from the age of 15. I m 19 now. I ve dandruff too. The dandruff forms in clusters. And are very stubborn. I just cant get rid of them. I need to shampoo my hair after every two days otherwise it gets very oily, dirty, full of dandruff and itches alot. I find hairs every time I run my fingers through them or comb them. I never used any colurs or chemicals. Never straightened them. Used gels twice of thrice in my entire life lol. Had long hair before ( not more than 2 inch) but I am keeping them short for the last 6 months. But it didnt help much. I dont do any hairstyles. I have bald spot on front corners of my head and the hair round those area is thining aswell. My hair scalp/root hurts recently. Dont know why. Other info: I used to weight 50kgs when I was 15. Now I weigh 65kgs. I dont ve any other symptoms or suffering from any illness. Not taking any medications. I dont eat vegetables much. I dont use any sort of oil on my hair. I had very thick hair. Which made styling almost impossible. I still have thick hair but less in amount. I do have acne. No one on my father s side or mother s side is bald. I just want to know what is causing this and how can I prevent them. And I jst want to get back my head full of hairs just like before I met hairfall lol. Thanks in advance for any sort of help or info :)