Hi,
Everyone before me has given great and truthful advice. It all comes down to you. You are the only person who can change this mess simply by extracting yourself out of it.

Get yourself REALLY busy. Join classes of something that interests you, like dancing or art or web site builing , or yoga... I guarantee you'll meet some other people and might even make some new friends. Create a commitment to yourself, not to a married man who is blatantly breaking the marriage vows he made to his wife. He is a manipulator of the worst kind and it appears he is playing you well, however what you get by accomodating this guy is lowered self esteem, and worry. Is it worth it to you? Honey, life is too short and there are good men out there. Dont be wasting your very precious time on this one.

My Mom has a great saying....the easiest way to forget a guy is to find a new one...
and in order to do that, you need to make yourself emotionally available.

Best of luck to you!