Hair loss

What are some reasons why I might be losing so much hair? My hair was really thick about a year ago and I’ve noticed that a lot more of its falling out.

I wash my hair 2-3 times a week, I dye it maybe every 3 months and rarely use any heat on it. I know that there’s a lot more that could contribute to it. I don’t really eat too much, I’ll eat a full meal maybe 2x a week, the rest of the time I just have a snack here and there. I’m not great with my water intake. I’ll drink maybe a bottle of water a day, the rest of the time I just drink caffeine. I got blood tests done about a year ago when I was admitted to the ER and everything looked normal.