Why is my hair shedding like crazy?

I'm a 22 yr old woman and I have fine midback hair and for the past few months a ton of hair falls out. i know its normal to lose about 100 hairs per day but everytime i put my hair up in a loose bun or pony tail and then take out the hair tye at least 20 hairs tops come out and when i take a shower and dry my hair around the same amount comes out. i always seem to have a bunch of my hair on my clothes or pillow. even when its layin flat ill run my fingers thru my hair and it comes out. i hope im making sense but it seems last month my hair was way thicker. also i have had a dry scalp lately but my hair gets super oily. i'm anemic but i've never had this problem before.. i started to use anti breakage serum so obviously im not gonna be able to tell if its working just yet. but am i going bald? whats wrong with my hair?