I agree with supermom you need some help here and advice so go to the school counsellor ,ask an expert what you can do , make sure you are busy with your studies and any work , keeps your thought positive look to what your Goals are for your future, you are adult, you are moving forward ..Good Luck
You need to get help for sure, is the any other family around you that can help you out? Maybe trying some counseling for you and your mother both. Is she willing to listen to you or anyone at all? Now that you're 18 yrs old, you do have to start acting like a adult but at the same time, at the right time, you can still have fun. If you are ready to be on your own, then do it. But make sure that you have a job and are financially set to do this transaction. At the same time, you also need to be emotionally and mentally ready for the bigger world outside of your mothers door. I was in the same type of boat that you are in now. I never got a childhood because I had to be too busy raising my mothers children but when I decided to go out on my own, I grew up quickly because I had bills to pay and rent and food to buy and employment to find and keep. Do you think that you are ready for all of this responsibility? If not, your mother may have a point. Have you ever just sat down and talked to your mother and told her how you feel? No games or anything. What changed in your life that made you not have a childhood. Why are you afraid of your mother? Do you honestly think that your mother would hurt you? You need to sit down and think about your situation carefully. You r the only one who can change your life.