we don't remember everything that happens to us. heck, i would be pushed to give you a detailed account of my past week, and certainly nothing bad has happened in it .

the research on memory tells us that all sorts of memories deteriorate (both good ones and bad ones). also, memories are nortoriously unreliable - every act of remembering is an act of creation - you pay attention to different elements of the event each time, and in that way, you kind of "reconstruct" your memory. recollection doesn't happen in a 100% veridical manner.

i guess i'm trying to reassure you that you are not "abnormal" for not recollecting large portions of your childhood, and nor does it mean that something "bad" happened that made you repress these memories. people who have full recollection of their childhoods still end up in therapy, and recollection and processing of every "bad" thing that happened is not necessary for you to achieve a satisfying life.