First of all, I understand that your life has been difficult and that things that not go the way you would have wanted. I am sorry you got bullied and your parents had a fight. But please, don't hate yourself. You might have done things that weren't right and that you regret, but what you hate is your behavior, not yourself as a person. You say you want to change, be a better person. You have already made the first step: You have realized what you want (or what you don't want). That is a huge archievement already, and it is the most important condition to become who you want to be! Please be aware of that.
Actually changing will not be easy and it will take a while. There are a few questions you should ask yourself to begin with:
You say you hate yourself. Why? What is it that makes you hate yourself? Which behaviors exactly? Keep track of what you do for about a week and write down what you wish you hadn't done, what you wish you would have done and also write down what you did well. Then define aims. It is easier to change if you make it concrete. Think about how to reach these aims, try to be realistic about it. Take it one by one. Remember, this a journey, it will take a while. And it is not a race.
All in all, changing is a process and if you are serious, if you really want to do that, you should get help. If you have family or friends who are willing to help you on this journey, ask them. Tell them what you want to do, how you want to change, ask them to help you. Ask them to tell you when you fall back in old patterns. Ask them to support you. If they are real friends, they will. If you feel like you are not making progress, or if you feel like you need more help, you can consult a psychologist. They will listen and support you, they know how to change someone's behavior. I know there is a lot of stigma about going to a psychologist, but basically all they do is talk and teach you tricks to deal with your problems.
Good luck. You can do this.