I know you're not big on compliments but I can't help myself when it comes to stating the obvious - you're wonderful and truly amazing. The proof is in your post. You're beginning to wonder about a lot, which proves you're wonder full and I'm amazed by your level of consciousness which has brought you here. With you amazing me, this makes you obviously amazing. You don't have to feel your wonderfulness or your amazingness, sometimes it can be enough to just recognise them in some way.
I can relate to the self harming, from when it used to be my 'go to' thing when I was about 16. By the way, I'm an old gal of 50 now :) Of course, people do this for a variety of reasons. I can relate to your reasons, that level of self hatred. For me it was mainly about a form of self punishment. If I could talk to my younger self, I'd say to her what I'd like to say to you: It is time to be an attention seeker, so that you can gain the attention of those who can guide you away from going into a depression. It is time to be dramatic and if your dramatic self can't get people's attention then it's time to be over dramatic. Wave your arms, scream at the top of your lungs or cry like a maniac 'I CAN'T KEEP DOING THIS WITHOUT GUIDANCE'.
If anyone was to say 'Oh, that person's just being an over dramatic attention seeker' and then leave it at that, I couldn't help but say 'What the hell is wrong with you, that you would make that statement and then leave that person to suffer?!' I'd have to control myself and not give that inconsiderate person a bit of a slap on top of it :)
Calli, who do you sense raises you in some way? Who do you sense brings you down? If you're sensitive enough, you'll be able to feel it. If you sense yourself being raised (your spirits and your level of consciousness or self awareness) by your school counselor, that GP approval may be worth gaining. If you feel raised simply by coming here for now, this may be a good start.
Calli, I know it sounds a little crazy but you'll want to being holding onto your sensitivity because it will serve you well. Don't let anyone tell you 'You need to stop being so sensitive'. If anyone tells you this and it leads you to feel down, that is 'the feeling' of being shut down. It pays to recognise this feeling so you can ask yourself 'What is wrong with a person who would want to shut or bring me down?' Sensing the questionable nature of others is a natural self esteem booster.
Come back anytime you feel the need :)