THICK TO NOW THIN HAIR... (HELP)

Hey guys, so over the past year I noticed that my hair has gotten incredibly thin, it’s so thin to the point where I’m afraid to brush it or it will fall out.

Now this is not the first time my hair got thin, this also happened in 2016 when my hairstylist kept using a hair relaxer on me to make my hair straight....

I haven’t gotten any relaxers since 2016 but idk why my hair is thin again :((( when it used to be so thick

Idk what I should do??

any advice or opinions/ stories will help greatly :)

Thank you!