Severe head itching and hair fall.

Hi. I am 26 and the reason um writing is for the past 3-4 months or more my hair is falling and thinning like never before. I always had thin hair but i never had a hair fall prior to this. It all started with some pimples all over my head which would go away after a few days and then come back. But after 2 weeks or so it stopped but not completely . I still am getting those pimples but 3-4 at a time . And for these 4 months i have serious itching in my head that i had never experienced in my life before. And my hair fall is uncomfortable no matter what i do. I had zero hairfall prior this incident. But now i lost all my hair in four months. For the past few days the itching is gone beyond control everywhere in my head and today i feel like it burns now but i don't have any pimple right now or may be a few. Please suggest me what i should do because this is giving me a mental torture because i am losing all my hair . I don't use shampoo regularly bcz any shampoo i use adds to my hairf