I have barerly started the game, and i get to wonder if my player character has lost his memory, since little is told about his past. its not actually told i belive.
Or did i miss it at some point? Or are we meant to be confused about why the man shoot me? Dont spoil please when you answer. im just looking for the general info..

In short, no he hasn't

In general, The Couriers past beyond delivering 'the parcel' was intentionally left vague for the people who want to Role Play, in Fallout 3 we were set to one background, but with your past an absolute mystery, it's easier to write your own character.