I can’t even begin to describe the emotions I went through as I read your essay. I’m so sorry you had to suffer through such horrible abuse, especially at such a young age. Abuse of any kind, at any age, is never ok, but the sexual abuse of a child is so much worse. Children are supposed to be able to trust the grown ups who are entrusted with their care. When that trust is broken it leaves the child lost, confused, and unable to trust again. Adults are no longer seen as “safe”. Sexual abuse of a child is simply unforgiveable.
I know you want someone to tell you what to do, but I honestly think this is something you have to decide for yourself. Despite everything you’ve told us, it’s impossible for anyone to tell you what to do without personally knowing everyone involved.
Since I know how frustrating it is to receive an answer like that, I will tell you what I would do in your situation. I’m trying to differentiate that from telling you, personally, what to do. Bearing that in mind, I can only form an opinion based on the information you provided. After taking everything into consideration, such as how deeply this has (and still is) affected your life and continues to affect your relationship with your parents, if I was in your shoes I would tell them. Again, this is only my opinion based on the information you provided.
In reading your essay, it sounds as if you want to tell your parents what happened, but you want someone to confirm that you’ve made the right decision. If that’s true, I would have to agree with you.