I pat you on the back for trying to LEARN about poly before turning tail and running. I am poly and one of my significant others is not. He knew nothing about poly when we met (and I told him about my being so right away), but he wanted to get to know me and learn about poly before making a hasty decision. It hasn't been easy for him, but he admits it was worth it. I wish you luck in your discoveries about poly and in your relationship with your girlfriend.
Sex between a man and a woman can be absolutely wonderful - provided you get between the right man and the right woman. ~Woody Allen