Hairs Falling Out?!? 😨

So I have RLY long thick hair, and my hair falls out like rly bad... like a lot comes out at once.... I shed worse than a dog in summer time. My SO tells me all the time that I should be bald by now. Is there something I could do to keep this from happening? I've tried different shampoos and conditioners and even different hair treatments, and my hair still falls out... help??? I have low iron levels and I use to have an eating disorder... could that be the cause of my hair loss???