Reverse deja vu??

Basically - my mum was an alcoholic. From what I thought, she burned down the family house years ago by being careless with a cigarette. Ever since I can remember, I've always known that it happened. In my head I can see it/remember it happening. I remember seeing her put down the lit cigarette and walk away. Ever since I was little I've told my friends about it, but because none of my family members had ever mentioned it, I always thought I'd dreamt it, so I never looked into it too much. Up until this year it's been my most vivid memory and I always tell people about it being a weird dream. I was taken away from my mum when I was very young, and she died last year from a fatty liver (alcohol overuse). Though I hadn't seen her for years, it hit me hard and I became suicidal. In February this year, I was talking to my dad about my mum and he said he couldn't listen because he can't bear hearing about her. Obviously I told him to stop being so disrespectful because at the end of the day she's still my mum. After this, my dad handed me divorce papers (all the reasons he got divorced from my mum) so I could gain a better understanding of why he was forced to get a divorce. One of the many reasons was because she "burned the family house down by being careless with a cigarette". So obviously I was like "Oh my god! This whole time I'd thought it was a dream and it's actually true!" Obviously it freaked me out a bit because I knew about it before I'd read the papers, but I just assumed I could remember it from my childhood. It's now July. I was talking to my boyfriend earlier about my mum and decided to re-read the divorce papers because it gives me a better understanding of things. I am so confused. It says my mum burned down the house in 1998. I was born in 2001, 3 years AFTER the house fire. I wasn't even alive to experience it. My whole life I remember it happening and I remember seeing it. It's my most vivid memory and I wasn't even alive when it happened. It's creeped me out because I knew it happened before I found out that it actually happened, and turns out I wasn't even there. It's weird because it happened before I was born but I remember being in it. I knew that it was my mum that did it and I knew that it was caused by a cigarette but no one had ever told me. So I asked my family if maybe they'd mentioned it to me when I was little and I'd just forgot and assumed I'd dreamt it. They said they made sure to never mention it to me because they thought I'd freak out about it. So if no one ever told me, how did I know it happened? How did I know how it happened? What does this mean?!