What shoud I do?? I'm hurt!?

My so called "best friends" are turning their backs on me now that we are older. My best friend or as I call "my sister" wrote a note to a girl talking about me behind my back. I've been "best Friends" or "sisters" with this girl since 2cd grade, nd we've been there for each other ALWAYS! and my other so called "best friend" got into an argument with me because I told her how I felt about her just dissing me for another group of people. We made up and I let her borrow my wii game (which I really wasn't supposed to) but that's what best friends do right??? And my other best friend hasn't talked to me much anymore. They have been meeting up at one's house without me, or without even telling me. They have been hanging out without me. But I have to be at home alone (the only KID in the house) wondering what they are doing, try to call them, ask them to hang out with me, and try to be a best friend, but all I get is this!!! It's ******* bad enough that I'm going through things, this just adds on, what should I do??? What do you think??? Please help me, because I feel like crying, but I'm trying to be strong because i cry all of the time, and it SO doesn't help me with anything! I'm hurt SO bad. What do you think that they are doing???