Like others have said, I also want to give you a huge hug.
It really, really isn't that bad. I'm sorry you were punished so badly for it by those who should have had the sense to ask you what was going on.
It sounds like you've been traumatised by the incident and are finding it hard to let go as your brain wants to process it. It's this kind of thing that can respond really well to therapy as a good therapist can help you process it and move on.
The story on its own sounds not nearly as bad as things my friends have told me with humour, along the lines of "OMG, I was terrible as a teenager, guess what I did! I did XYZ, can you imagine? My poor mother/friends etc!" but no on thinks they're like that now.
I wonder also if maybe you might have rejection sensitivity dysphoria? I have ADHD and I've been reading up about it, but I think it may be something you can get with ASD also?
It's hard to deal with rejection if you have RSD, it can make you really hang on to it and not know how to process it. RSD can be triggered with perceived rejection. However you experienced a whole lot of actual rejection from those who should really have been concerned for your feelings. I wonder if that's made it harder for you to process. Just a thought, perhaps something to think about.
www.additudemag.com/rejection-sensitive-dysphoria-adhd-symptom-test/
wasntsuchasweetsixteen, please have a think about how to start working out how to forgive your 16 year-old-self for this, so you can move on. It's a ghost of the past that you need to banish back to the past where it belongs, it has no business in your life now.