Extreme hair thinning. Is able to fin?

Hello docs, I have been facing extreme hair loss since 3 years now. I have visited the many reputed dermatologists in Noida/ Delhi. I tried a lot of serums, shampoos and what not but nothing seems to work. It stops for about a month and so and then comes back. Recently I had blood test done and I've a lot deficiencies like lack of Vit D, B, iron and a lot more. So I started taking care of my food habits. It's been few months I make sure to eat protein,fibre, basically everything that could make it stop but it looks like there's no stopping to this hair fall. I used to have really really thick heavy tresses and it's all gone now. I barely have any hair left on my scalp. I still do have long hair but extremely thin, I'm so scared to tie them up now that I always keep them open. This is somehow taking a toll on my mental health too. This is too scary to watch lose so many hair strand's every since day. Can anyone help me please. Could be any underlying condition that no one is able to fin