First off, I'm sorry that you have to deal with this. It's a traumatic experience, but life is one of the most beautiful things, because we only get one. And you're never alone. You've already taken a huge first step by going to therapy, and talking about what happened will come naturally. You never have to say anything you don't want too, and that's perfectly okay. Some people just need the right person to listen first, and coming here where there's tons of people is a good thing.
But hun, cutting isn't healthy. And I know that is something most people already know. Don't be mad at yourself for making those choices though because we all have to learn. I understand that it's a way for you to get out your anger or just because you want to be in control- but maybe that's one of the first things you can work out with your therapist. If you don't want to talk about what happened w/ your step-brother, you can work on helping control your urges. And if you haven't told your therapist that you've cut, maybe telling her that will open door to talk about this incident. Maybe you've heard this before, but what happened to you doesn't define who you are- you choose what you want to become.
I'm always just a
PM away Meg.