That's pretty much how all my conscious thought takes place - like a narrative. Sometimes carrying out dialogue like you say. I spent a lot of time on my own as a kid and it was like having an invisible friend or fantasy world. Maybe out of boredom. It's never bothered me though, once I asked all my friends (sane ones too) and they all thought in the form of conversations etc. It's when you spend all you time on your head trying to 'prepare' yourself for life rather than living it, when it becomes a problem, or as a way of escaping some hard facts in reality that may be too daunting.