Please go to a dermat. Get a blood test done. I know what are the likely reasons ... But don't want to give medical advice on the internet.
In the meanwhile, eat Vit B12 rich food. I am applying garlic water to my scalp every 3 days a week.
Take 100ml water in a glass bottle, slightly crush one clove of garlic and immediately put it in the water in the glass bottle and shut the lid. Keep it in sunlit area for 2 days, then apply this water to your scalp. Dont go into the sun with it.
After the 1 st use itself, my hairfall drastically reduced. I loose like 10 strands a day max.