I had the urge to cheat on my girlfriend and I actually tried to do it.
Why would you do something like that to your girlfriend?
To experience the thrill of cheating
You should be faithful to your girlfriend when you are in a relationship.  Even if you just wanted to have some fun, and didn't really want to break up with her, it was still wrong of you to cheat.  If she found out, she would be justified in ending the relationship, and you don't want that.
Why, I can do what I want. I'm a free man, free myself. I just want to experience and explore new things.
If this is how you really feel, then you should break up with your girlfriend. There's no reason to drag her along and cheat on her. Doing this will emotionally affect her greatly.