how to talk about sexual abuse

I need help. years ago, something happened to me when I was 13, but I can't recall what. 13 year old me says my grandfather touched me inappropriately & tried pulling my clothes off. 22 year old me doesn't know anymore. I was never properly educated on sex, I'm unfortunately self taught. I'm still very confused on the situation. I still don't understand...

My memories are suppressed and replaced by multiple rapes and acts of physical and sexual abuse by my high school boyfriend.

I can barely recall what happened when I was 13.. And my parents are asking me to talk about it because my grandfather has unexpectedly re-entered our lives... they are wanting to help him, but don't want to hurt me in the process. But I'm not wanting to talk about it, but I know I need too.

How can I talk to my parents about this if I don't have all the facts and can't recall much more then what we already know?... the other times it was brought up, I wad told I was wrong because I didn't understand..