That's a tough one. I don't think I really told anyone about my SI, they just saw it. After a close friend knew, I'd call her when I was feeling the urge to SI, but most of those calls went unanswered...So now I just don't talk about it at all and do my best to cover it up.

I would suggest telling him before Christmas. You might be surprised as to how helpful he could be. It would give you someone to talk to when you feel you're reaching the point of SI. I assume its worse when you have no one to talk about it with (for me at least). Then there isn't anyone to try to stop you...