If someone else, either a sibling in the same household, or anyone else with your activation key, has logged into the game, they may have changed the name. Which, of course, means it will be changed on yours.
Just ask any of your siblings, or anyone else who has access to your computer, if they've changed the name. If they have, just change it back and beat them ask them politely not to do it again.
If they haven't done it, I suggest PM'ing Badspot to check the IP Adresses it has been logged in on.
If one of them isn't yours, then that's your problem. Some one else may have access to your Authentication Key.
If that's happened, your key will be deactivated, and you may possibly be given another. I wouldn't know for sure on that.
Just make sure you haven't given your key out to anyone, either in person or online. Also make sure that no siblings have had your key, and shared it to someone else.
Also, just to be 100% sure, you haven't changed your name yourself, and forgotten about it, have you? You don't want to have your key de-activated for no reason.
