I had an ok childhood up to the age of 8 or so, but don't really have access to it. I didn't realise this until one day, T and I were telling each other stories and she asked for a story from my childhood. Instead of looking back at my life, I realised I was turning the pages in the photo albums of my childhood, as if this was my only window. Later, I realised that probably wasn't 'normal'.
I think for me this has happened because I received very damaging 'treatment' in my early teens which effectively rewrote my childhood into lies. It took away something quite fundamental, and even though now I can separate truth from fiction, I don't feel like I ever got back the childhood I lost to that treatment.
I guess this doesn't help you much- sorry. I just wanted to empathise about how hard it can be not to remember, and to wonder why you don't remember etc.