Welcome Jellyfish. It sounds like you have a difficult dilemma with your friends, but their treatment of you is definitely not okay. It sounds like they may even be crossing the line into bullying if it's causing you emotional distress, although I'm not entirely sure what it is that they are doing so I won't make that call. Either way, PAYNE is right; perhaps talking to a school counselor would be something to consider. They might be able to help you sort out how to deal with this situation.

As for Billy, well...I hate to say it, but guys can sometimes be different with you when you're alone with them than they are when they're with their friends. It's unfortunate, but it's true. It usually has something to do with the age factor, although some guys never outgrow it. Anyway, maybe you should ask him about why he does this and see what his response is. It doesn't seem to me that a very good friend would only treat you like one some of the time.