Do you ever wonder if the things you remember going through as a child really happened?

I never doubted the CSA until a few years ago when I finally told my family and was called a liar and my dad told me I probably confused normal curiosity with SA. Even though the abuser is 8yrs older than me. I *knew* it was wrong and wonder WHY I let it happen. I'm confused and wondering if what happened REALLY happened or if I am a liar. How can I remember things in detail and yet be told I made it all up?! I kept it all inside for 18yrs before I told someone I trusted. I feel like I've ruined HIS life by accusing him of this. I feel horribly guilty.