I am so very sorry for what you have gone through.
If your mother relapses, it will not be your fault. It will be her choice. Please know that you are not responsible for her sobriety.
Please do seek help for yourself even if you think it will upset your mother. This is your life and you know that you need help in order to get back to school and get a good job. You do not need to give up your life in order to protect your mother.