Just tell people what you are comfortable with. When you have your assessment the staff will ask about self harm if you can't find the words show them the cuts- that's what I did. If it was your GP who referred you then they will already know something. As you have a child they will have to ask some questions about safety, they aren't trying to put you in hospital just to make sure you all stay safe. Not turning up will make things harder so please try to go, even if you go and then don't say much.