You may think you are emotionally connected with him, but how do you think his girlfriend thinks she is connected with him? What does he say to you vs what does he (really, not just what he tells you) say to her? Who is he going home to every night, who does he kiss every day, who is he sharing his entire life, family and love with?

Do the thoughts of him and her disturb you? Because he's told you he's not leaving. Do you really want to be a mistress your whole life, because you are.

How did he and his GF get together? Do you really think with the circumstances of your getting together that you could really trust him not to do the same to you?