"Shooting stars", I agree with Karrie about getting a Ferritin blood test. When I unknowingly had low ferritin, I was losing loads of hair and some of my fingernails developed verticle ridges --- plus I had terrible brain fog.
My MD thought everything was fine despite my complaints. However, after suffering for months, I returned for an annual routine blood test and when my primary care doc saw that some of my blood levels (e.g, hematocrit, hemoglobin and iron) were below normal, he finally ordered a ferritin test. Fortunately he referred me to a hematologist who prescribed iron supplements and tested me every couple of weeks, until all my levels returned to normal and around that time, the brain fog left and my hair stopped falling out.