NLS - my advice would be not to do anything about anyone at the minute. You are in a truly, truly difficult place and changing your external situation won't change that - it may even bring in more problems for you to deal with - which I think is sometimes why we do it, because it means being able to focus on something other than that awful pain.
Don't email your principal. There is very little chance that he will do anything positive and may well blame the whole thing on you or claim you are making it up. You don't need that at the minute, you already have enough to deal with. Write him letters that you don't send, to get it out of your system, but don't mail him anything. Focus on you, not him.
Don't contact your boyfriend any more today. I know how hard it is, but every time he ignores you it will make you feel worse. I don't know what the situation is at the minute, but you need to focus on you, not him.
Your ex is an arsehole. You don't need to prove anything to him, your mum or anyone else. You haven't done bad things, you've had bad things done to you, and that isn't your fault, NLS, there are some sick, twisted, nasty people in the world and they do bad things to people just because they can. There's no rhyme or reason to it, it's not down to you or anything you've done, you were just very, very unlucky. When your parents aren't protecting you you are vulnerable and that vulnerability stays with you. But you are changing that. You're working through all of this, you're pulling off all this stuff that's held you back and made you feel bad and peeling away all the crap you've been brainwashed with. And underneath it all is NLS, sweet, brave, smiling NLS who will get through all of this and come out of it the other side healthy and happy and feeling sooooo much better about the world. Your ex will still be an arsehole but it won't matter because you'll know your own truth and whatever crap he spouts, you'll know it isn't true and you won't worry about it.
Cry the tears. Let them out, even though it hurts. They clean you out from the inside and take away some of the pain and it does start to feel better. Don't think about your mum and her thoughts on your relationship. It scares me that she says 'we' can find someone else. Focus on you, you, you - not anyone else. Your thoughts, your feelings, your pain, your anger. It's part of you, part that needs to be heard and listened to. (((((((((((((((((NLS)))))))))))))))))))))))))))