If you think things can't get worse it's probably only because you lack sufficient imagination.
I think you are entirely too young to be so involved with EITHER girl. You are in high school so you need to have other experiences.
Don't use the excuse though that you don't want to break up with your girl friend because you don't want to hurt her. Just break it off and move along. Whether the "other" girl will be available or not isn't relavant. Staying in a relationship for the sake of a relationship is cheating youself and your girlfriend. It's also a bad habit to start. You talk about your maturity level and I am here to tell you that ending relationships is hard, but it is the mature way to handle this.
Stop thinking you need to be tied to one person. You are young so experience life and when you are ready to settle down with the one person who really trips your trigger...you'll know.
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