Help making more close friends?

I'm in 8th grade, leaving in a month for high school. I've been at this school for so long and it seems like my close friends are migrating away and shifting to my other close friend, Carla. Carla is kinda my competitor at the same time... but we love each other like sisters. I wanna be closer to these girls and I admit lately I've been very quiet and I don't even know why! Stress? Anyway, what attracts teenage girls to be friends with others? I play sports, sense of humor, got a boyfriend, I don't know whats up!? By the way, there are only 50 kids in my class, 30 of which are girls and only 20 have anything in common with me once so ever! Thanks for the help!