I would think it might be anaemia, as my hair was coming out, not in clumps but when I'm washing it and running my hair through it, there is more than usual if that makes sense.
I would ask your doctor for a blood test to see if you're anaemic. Ive got these things called spatone iron water and you add it to a glass of fruit juice. This is instead of taking the tablets as they really didn't agree with me
xxx