Being the other girl....

Ok, ladies. Here's the sitch. I know, I know. I'm a terrible person and I need to learn my place. I'm the other girl. However, I don't need you here to tell me how much of a terrible person I am. Because I know what I did. I'm here to ask you what the heck is going on. 
The guy that I was seeing who yes, did have a girlfriend, kept telling me he loved me. It then got to the point where he told me that he was in love with me but because of the situation with the child, he did not feel comfortable leaving his current girlfriend. And that if the circumstances were any different, he would be with me. I remind him all the time that everyone knows that his intentions will never be to leave her for me because that's not how it works. However, he explains to me almost every day how much he loves me and cares about me (which seems untrue because he's still w/ her.) and that we just click on a whole other level. He's told me that he knows now what he should have been looking for in a relationship (talking about me) but he can't do anything about it right now. I would never be with him, because he would probably cheat on me, too. However, I just wanted to know people's thoughts. Has this happened to you? What did you do? Do you think you can love two people at once? Etc... Just curious. (we no longer see each other, however, I still think about him occasionally.)