I cheated on the woman I loved.. but did I?
Did you cheat on your girlfriend or not?
She cheated on me first, so I have the right to.
Even if your gf cheated on you first, that doesn't make cheating on her correct. Address your issues with her cheating, instead of making things worse by doing the same to her.
I don't think I cheated on her, she just slept with my friend.
Well then what she did is wrong. She shouldn't be cheating on you in a relationship. How do you feel about this?