I believe that you should end it. I think the only reason your with her is because you think you love her but it's just the resentment that is holding you back from leaving her. WHATS LOVE IF YOU BOTH CHEATED ON EACH OTHER??!! Were is the love? Its the best for both of use guys. Trust me!
You guys are young teenagers, no need to stay in a destructive and meaningless relationship. Bring up the courage, end it.