Hi,
I feel the pain and loneliness you're going through. I hope you don't start cutting again.
You'll soon be an adult and can make your own life.
I know how you feel about your adoptive mother, however feelings can be deceptive. Your problems probably started before you were adopted. You may not be aware of it but your dislike to your adoptive mother is really directed at you neglectful biological mother.
Try to be tactful and make peace with your adoptive mother. I'm sure things will turn better for you. Your situation was caused by your biological parents.