Its hard to feel good about yourself when you never get the validation you need... I know... I excelled in music yet my parents never praised me or showed any pride...
I was teased in school too and now it doesn't matter in my life... I agree with Sky that you should show your maturity and talk to this teacher about giving you the respect you deserve.I am a mom.
I have a son who is 16 and once when he told me a teacher had ridiculed him in front of the class, instead of going to the school myself I told him he should politely tell her how it made him feel when she did that and that he didn't appreciate it and to ask her to not do it again.
Guess what? She respected him for coming to her like that and she never mistreated him again.
Maybe you will have to go above her to the principal.. maybe not. but I assure you that by standing up for yourself in this way you will gain a little confidence.
You must be quite the survivor to have overcome an eating disorder...to me that shows strength and courage most of those other kids at school have no concept of.Keep your sense of humor... it helps.
As for purpose. i dont'know how old you are but my son has no purpose except to enjoy being a teenager... he is all about having fun and living his life...he works enough to keep his car on the road .. and to pay his cell phone bill and he spends his spare time skateboarding or playing pool... hangin out with his friends...thats it.
He doesn't have a plan for career or college.. he can't even answer the question of what he wants to be when he gets out of school.I think some kids ( if truth be known about it) have the purpose their parents give thm.. they plan what their parents want for them.
Don't be so hard on yourself... nobody is perfect.. some can pretend they are.. which is what I tried to do... but there is no such thing...we all are human and as such make stupid mistakes and poor choices all throughout our lifetimes.
Be yourself.. that is enough. and one day it wil even feel like it is enough. Wishing you the best...Faith