You know you're a nerd when one of your Heroes is Lord Sheogorath of the Shivering Isles.
You know you're a nerd when you can have hours long discussions of what kind of Jedi you'd be and how you'd use your powers.
You know you're a nerd when you've had hours long discussions about how you'd take over the Galaxy that is the setting of Star Wars.
You know you're a nerd when you've had hours long discussions about how you'd take over this world.
You know you're a nerd when you'd rather read a book than watch a movie, any movie.
You know you're a nerd if you've ever had an argument about which is better; Vampires (I'm talking about Vampire Lords and Vampire Regents here), Werewolves, Jedi/Sith, Wizards/Witches, Mutants, or Benders/The Avatar.
You know you're a nerd when one of your favorite things to think about is just how much face your D&D character can wreck. And how OP you can make him without it being ridiculous or game-breaking.
You know you're a nerd when you can't help but fanboy/fangirl squee when you find a Word Wall with an additional word to one your favorite Dragon Shouts in Skyrim.
I could go on, but I'll stop off here...
12 years