I agree with ^. You need to tell your parents, a school counselor even. They care about you and want what's best for you. Maybe you could go to a doctor about the panic attacks?
I know that they have a thread here about alternatives to
SH, and that is something you should check out. I know that I personally like to punch pillows. You could even try the butterfly project, that helped me for some time. You know, the whole draw a butterfly where you want to cut, but if you cut it you kill it? That helps if you like butterflies.
To deal with the urges, try thinking of someone that you care about very much, and how they wouldn't want you to do something like that. This is what I do, and it helps me a lot.
Remember, you can
PM me anytime ok? <3 and