Oh Peter. This is my first post on Mumsnet as I just had to reply to you. It could have been me writing your post and, whilst I don't have any advice, I can wholeheartedly relate to what you are going through.
I discovered last week (through stumbling across his open facebook account) that my DS 13 has been discussing self harm at length with a friend who has self harmed for some time. He has made a couple of attempts at hurting himself (but luckily at this stage wasn't successful). Through this however I have discovered that someone who I have always believed to be a happy-go-lucky, relaxed, confident and well-adjusted boy is actually someone much more complicated underneath. It is deeply distressing to learn that your beautiful, precious child wants to hurt themselves when every essence of our being as a parent is all about trying to protect them. It has quite simply brought our whole word crashing down around us and, like you, I feel helpless, useless, miserable and am wondering what the future will now hold.
He feels he is anxious and depressed which is also devastating and, to me, feels like a terrible reflection on our parenting skills. How did we not know this was happening? I keep wondering if we did something wrong, were we too strict, not kind enough, thoughtless? Things I had never considered before but which are now spinning around in my head every minute making me sick with a feeling of deep dread in the pit of my stomach.
On a more positive note, DS has just had a session with his school counsellor which he found a very helpful experience. He says it was good to talk about things openly and put things in perspective. I have also spoken with his form tutor who is lovely and will be keeping an eye out for him at school. We have also made an appointment with our GP to see what advice he has.
In the meantime DS has pleaded with us not to allow every day life to be any different, he is so worried things will change and that we will be walking on eggshells (which obviously we will!). So we are putting on our happy faces and are carrying on as usual which he says really helps. We also encourage him to spend more time in our company rather than in his room alone which, surprisingly he doesn't actually object to!
It is so good to know we are not going through this alone. I really hope that things improve for you and your daughter soon and I really can't put into words how much I am feeling your pain.