When I was 13 years old I did something very wrong. Back in the day in my middle school was fucked up trend: slaping girl’s asses. I didn’t have the courage to do it myself so when we had family reunion I decided to practice with my 5 years old cousin. When I was playing with her I slightly spanked her butt over the clothes multiple times. Then I continued with slightly pulling her pants down and then I slightly spanked. Once I had pulled so much that I saw her private parts and in that moment I had realized that I messed up. Since then I have never repeated such disgusting behaviour, yet my guilt and selfhate for this action has been slowly increasing.
Nowdays with my cousin I have good relationship, I sometimes help her out with school work. She doesn’t seem to be uncomfortable around me.
Am I a disgusting person?
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.
Would that actually benefit her?
Oh fuck no. Don’t apologize to the girl or you WILL have something even bigger to feel guilty about. How much random shit do you remember when you were five years old? I guarantee she doesn’t remember a bit of it and never will, but you could easily plant false traumatic memories in her brain. That’s just fucked up every way you look at it.