Oh Emma, I'm so sorry to hear how bad you're feeling. You mustn't be too hard on yourself for being naughty because ANYBODY could be in your position right now. If you're feeling bad for what you've done, then obviously, you're not that big of a b*^ch.
There have been times when I've had a horrid time with my mouth: stepping in it and saying things I shouldn't. Then, I'll blow up and say the things that I usually just think, but never say.
Sometimes, for whatever reason, I'm just not in the mood to put up with somebody's crap. Plus, if I'm having an extraordinary amount of trouble in my life, it seems to make me more openly honest than I would usually be. Although, I have to admit, that the ones I usually give it to, deserve it! Ha ha.
This part of me seems to come out, when I'm at the end of my rope and had enough of something. Sometimes, we're just not in the mood for any bologna, know what I mean?
Maybe you're just in a difficult spot in your life right now and it's manifesting itself this way. Whatever the cause, don't lose hope! The fact that you're doing introspection is a good sign. Maybe you could fix some of the things you think you've messed up. If not, then you have to move on and be strong. Life isn't over and you're too young to throw in the towel.
I don't think you're a bad person at all. You've been very kind and helpful to a lot of people on this board, (including me), so maybe you're just in a bit of a depression right now.
Things have a way of working out and the fact that you're wanting to make things right, is a good sign.
Good luck to you,