Hey! I am also the daughter of an addict! It was so bad she ended up abandoning me to pursue a life of alcohol. She has been arrested over 80 times and every few years she tries to contact me which really makes me sad.
Your mother has fallen to her addictions and you should forgive her for it. Forgive her for being weak and understand that it is not about you unfortunately. Your low self esteem may have something to do with the fact that your mother chooses alcohol over you... This is something that bothers me too and my self esteem is so low! I have horrible anxiety and I never feel good enough. I am not confident in my decision making and although it's something I still work on it follows me. The last time I saw my mother over 15 years ago was really awful. She shook me and asked why her daughter was so fat and ugly. I was only 10. She was drunk.
I always feel that if my own mother doesn't care enough then why should anyone else. It's sad but a lesson to be learned is that so many people in life will disappoint you. Not all will and Its because life is tough, not because of you. You need to go out and get over this because you are a person who can empathize with others. You have faced adversity and with that you can help others in day to day activities of life. Be the person you always needed to other people and more importantly to yourself. You have no reason to be ashamed or worried. Believe that good things will happen to you and they will. Myself I have not gone to therapy and this still bothers me. I'm not sure if therapy would help me but I live fine and no one even knows what's really going on with me. If you think that therapy will help you then you should do if.
You have a chance to be different and you should give yourself that chance.
Stay strong and go out and take baby steps!!