I think you did fine. Your T wont hate you or be angry. They know it is difficult to get things out. You can still tell more next time. It's okay. Just tell your T there is something I need to say, then just say you self injure or you cut, just say it and get it out. Your T will ask questions probably after that and that will help you. Try to be as honest as possible. Your T is there for you, to help you.