I have a white mark on one of my teeth too. I have no idea how it got there but it's barely noticeable. My teeth aren't amazing; they're pretty average. They could be a lot worse though. They're not 100% white (not many people's are), so I might get them whitened one day and then I'd be happy with them!

I did wear a brace for a couple of years. They straightened them a bit. They're not perfectly straight now, but they'll do.