(((Welcometothejungle))) I also agree with all the above. The great suggestions of school talking to your parents, leaving letters to your parents. YOu do need help!!
I don't know know if you have any past trauma or these feelings may be there anyway. Do not let anyone drop the ball on this, you need help & sounds like you may have to fight to get it. YOu don't have to linger in this pain, it is not healthy to mask your agony in front of friends & who else you don't trust.
You say you have been asking for help since age eleven. That was very brave of you, but you need to ask again & be honest. Whether it's school counselor, school nurse, your reg doctor or straight out to your parents, it's time to tell them again you need & want some help.
You are not alone in your struggles, but life can really be so much better.
Keep reading the forums & keep posting!
Sending many kind & hopeful thoughts your way.