There is a possibility for you to be his one and only, but you have to play this right.
First of all, DO NOT tell his girlfriend about your relationship with him. Second, do not make him choose. Both of those recipes will result in a loss for you.
Do understand that he’s cheating on her, and he may cheat on you at some point down the line — unless she’s not a long term girlfriend, and the understanding is [i]or should be[/i] that they’re just dating without a commitment. You’re getting to know his character, and you should decide if this is someone you want to invest in because you’re getting emotionally involved.
Next buy and read my book, Think & Date Like A Man. You can get it here, and it will help you play this just right. [url]http://www.askapril.com/relationship-dating-advice/think-and-date-like-a-man.html[/url]. This books is written for women who want to GET the guy they’re after. So everything you need to know is in here.
Let me know if that helps. 🙂