I have created this thread to reply to this post of yours: http://www.scarleteen.com/bb/viewtopic.php?f=5&t=5355.
It sounds like you are noticing some trends in who you are sexually attracted to. You are noticing that there are people, both men and women, of certain ethnic groups you find yourself especially attracted to and also men with behaviors that you read as gay that you find yourself especially attracted to.
You asked if this makes you pansexual. Ultimately, it is up to you what sexual identity feels right for you! Pansexual is usually used by someone who feels attracted to people of all gender identities, or who doesn't experience gender as a major factor in their attractions. Does this sound right for you?
You asked, "What's happening to my brain? I was totally straight when I was thirteen!" Given your age, it makes a lot of sense that you are learning a lot about your sexual attractions right now. I want to assure you that if you settle on feeling not straight, that is totally ok and normal! Though I know there are a lot of heteronormative messages in our world, meaning messages that make it seem like being heterosexual is what is "normal" or "best"
Here is a piece on sexuality that will give you some more info as you explore all this: The Rainbow Connection: Orientation for Everyone.