As the dirty chat and have a "normal" quit convo with him online?

I saw him ard in my study time may by his gf. It was easy to talk to him too cos' we both have the same interest in music and entertainment continue to flow naturally. Days after dat i have him in msn. two days later we talked and he got bored so entertain me with a "grown-up story," and he enjoyed it. Since then, things abit completely out of hand when a "dirty chat" topic was brought up by accident. He confessed that he had a lot of fantasies about me. I think he didn't get much of 'that' attention away from her. A few days ago we had sexchat serious and if we both had fun that night, I still feel the wrong as he got gf already. feel abit of him as a cyber-sex partner recently, eventhough he made it clear that he likes me (in dirty chat room?) not quite sexual play. I would really like a friend chat to friends and tries to prevent free dirty chat theme to pop up.