Although I can’t make a diagnosis on the basis of a letter alone, I can tell you that what you are reporting is consistent with depression and perhaps social anxiety as well. You are reluctant to tell anyone about your feelings because you are terrified of being judged. Unfortunately, there are people who will do exactly that. But such people are ignorant and unkind.
You know as well as I do that if you could handle this on your own, you would have done so already. Five years is a very long time, especially as a percentage of your life, to feel miserable. You’ve already found that self-harm may distract you but it doesn’t make the feelings go away. You do need help.
Since talking with people is so hard for you, it might help to start by talking in a way that is more anonymous. The hotline run by Boys Town has counselors on duty 24/7 who are available to talk with teens confidentially. Don’t be put off by the name; girls can call too. Their number is 800-448-3000. You can also visit their website. Please look into it.
I wish you well.