Listen, holmes. I'm gonna bite and engage on this. If this turns out to be some elaborate prank, then I'll play the fool. It's whateva.
Probably not a bad idea; if we go on with this for too long, we'll derail the point of the thread.
I was thinking about this a bit while I walked to the store earlier, and I surmised that I feel like you're trying to get a response here in the hopes of externalizing some of the self-hatred you're inflicting upon yourself for what you've done. While that's certainly more positive a path than simply stuffing it down or trying to justify it to yourself, you could do better. Here, you're more likely to just be hit with a lot of bile and spite to reinforce your self-hatred, if anything at all; as you've seen, most people don't even believe you because of your general disposition.
I would instead encourage you to do what too few do: try to understand yourself. Really examine the how and the why of what you did. You've already accepted that it was foolish and wrong, but that's only the first step. Stop there, and you probably won't change anything. Change nothing, and you're just a time bomb waiting to go off again.
I sense that I am younger than you by a shade, but I have lived the past year under the weight of a sin of my own. I learned very quickly that no one--neither the systems designed to punish me nor the people who actually care about me--was truly equipped to instigate a change that would prevent me making the same mistake again. Everything that's happened to prevent a recurrence has come about by my own hand. While others can inspire you or offer suggestions, in the end, each person must forge the self. No one else can do it for you. No one else is equipped for the task.
So, that's the best I've got for you, I suppose. Take pride in the knowledge that you are at least wise enough to recognize the gravity of your mistake and let that pride push you toward a better self. It is, unfortunately, the only path a human has to transcending the limitations imposed by our animal nature.