How to deal with "gay" comments?

I'm thirteen at the moment, and you all know how middle school is. Whatever you do is marked as "gay" if they think it's weird. The problem is I'm bisexual and these comments really make me uncomfortable. I've tried telling the people that say it to stop without coming out, but they usually respond with "That's SO gay." How do I deal with these comments? (ps. im not ready to come out yet.)