I'm married but I recently met a guy- also unhappily married.I never let him know that I was not happy with my husband. He pursued me and called my cellular fone and left messages. We also saw each other to talk. In short, we had a physical relationship for only 1 time. He was kind and considerate and I thought we would see each other again. He still called a few times after but all of a sudden he just stopped. When I tried to contact him and asked why, he said that we both belong to someone. That he felt guilty and he'll just wait until my husband and I are not together anymore. I don't know if I should believe him or he just used me. I need an expert opinion because he really was very nice to me and seemed sincere.

He has a guilty conscience & so he doesn't want to go further in his relationship with you.
If he only wanted to use you, he would have carried on using you.

This was a one-time event; he is trying to be polite, but there is nothing further with this man. Move on and either try to repair whatever is lacking in your own marriage by professional counseling, or take stpes to have a trial separation. When you are unhappy and emotionally fragile, casual realtionships take on a far more significant appearance than they actually possess.