Sexual assault victim

So I just admitted to my boyfriend who I’ve been with over a year. The ONLY person I’ve said that too about a girl who made me do stuff to her sexually when I was a child... he was very supportive and understanding and I really appreciate everything however I got really ticked off when he said I was molested. It really bothered me... as a child I blocked it out and asked god to forgive me until I blocked it but then recently I saw the person who made me do it and now I’ve been having nightmares recently of what had happened. I know it happened but after actually saying it out loud i feel like I am making up a story. Even though I KNOW 100% what I said is exactly what happened. Why do I feel like I’m lying when I know what happened. I’m so confused. And these nightmares are terrible.. I wake up crying in the middle of the night