Memory Formation

[Elizabeth]

Well, let me put this bluntly. I was attacked about two months ago and have been trying to remember it ever since. My memory of it isn't so much of a blank spot as really blurry, as in, 'too blurry for me to know what really happened.' Then it occurred to me that if the memories never fully formed, (yeah, I don't know enough about neurology to know if memories can begin formation, then stop) then I really CAN'T remember it, because there's nothing to remember. So, my question is, which of the following factors could affect the memory formation process enough to make it impossible for me to remember?
1: I hit my head pretty hard at least twice that I'm sure of, although there could have been others. There was no bleeding that I'm aware of and I didn't lose consciousness; other then that, I don't remember if I got nauseous or anything.
2: My sleep schedule back then consisted of getting about 4-6 hours of sleep each night. That had been going on for about... maybe... three weeks?
3: I was oxygen deprived for around twenty minutes. Well, not really oxygen deprived as in I couldn't breathe, but in that I had a really hard time breathing for the duration of the fight, which lasted about twenty minutes.
I was sober, not on any medication, all that. Also, I never went to the hospital, so I don't exactly know my exact injuries, just that they weren't serious. So- with any degree of certainty, can someone tell me how likely it is that the memories were formed to the extent that I should be able to recall them?