Battling with reality

I only recently began to get flashbacks of incidents with my sister’s husband. I believe I was groomed by him and taken advantage of. It’s hard for me to come to terms with it because I can’t tell what was real and what wasn’t, Im scared because I cant remember the incidents with detail. I feel like it’s my fault and that I could’ve done something to stop it but it happened when I was going through an abusive father-daughter relationship, unstable living conditions, and also grieving the loss of my mother… I was vulnerable and was told i was “mature for my age” so I believed everything he said and did and even after saying no he would say “its normal, we’re family”. I was 16 and he was 30 and this went on until i recently moved away. I feel at battle with my own reality but I cant stop thinking about it and I’m legitimately freaked out. I dont know how to ask for help or who to talk to about it which is why I am here. I’m scared and I don’t know why