You did something due to peer pressure at an age when kids are obsessed with fitting in. In the course of doing so, you realized it was wrong and you stopped. Even now, presumably years later, you still feel bad about it. I'd say you're good, every single one of us has done things (often involving inappropriate actions) we look back on and regret. You're fine.

I hate to break this to you, but kids are idiots. Their brains are still baking, so they do dumb shit all the time.

There's a reason that kids have a separate prong of the justice system in many places. Everybody knows the sheer stupidity that can happen because they, too, have done abysmally stupid shit.

Now, this one was pretty fucking bad. But it's still just an idiot kid being an idiot, not some predictor of the adult the kid grows into remaining an idiot.

Mind you, plenty of adults are idiots too, but the ones that don't repeat a given form of stupidity are ahead of the rest. So you're fine. Let go of the guilt, stop beating yourself up, and move on.

Alright, so I'm going to be honest. This is a fucking minefield.

You need to take this to a therapist. Any unqualified advice here has the potential to be destructive.

Delete this thread and do not speak of this to anyone until the day of your appointment.

Your actions were disgusting, but you as a person are not disgusting. Even better, you stopped doing those things.

If it continues to bother you that much, consider apologizing to your cousin.

You clearly knew what you were doing was wrong, you've thought about it since and I'm presuming that you haven't done it since. Making a mistake and not making it again is the right thing. So no, not a disgusting person.

I didn't know that I have good advice for you - whether you should talk about it or just put it behind you - but be aware that 13-year-olds do some pretty awful things, just generally. It's that perfect intersection of dumb kid and new hormones. What you did at 13 doesn't define who you are today.