@Wondering333
I read your thread, and it is like you are writing a page from my life before I settled down and got married. I had this experience with several men, you think there was some connection, perhaps you were meant to be, you are unique to him and he to you but for whatever reason, he was with someone, or the timing was not right!
Looking back, none of these men was worthy of me, and they indeed were not for me. What is for you will not go by you, and if this man is meant for you, then he would not have married someone else trust me. I think in your case its more of a regretting something you never did than regretting something you did. You would feel happier seeing him go off into the sunset with his wife if you could say that you had a shot with him perhaps or got to experience was he was like in bed?
What is important to realise that these feelings you are having for him, are emotions and your emotions are not loyal to you. Your feelings change, adapt and grow over time and you are just mourning something you never had but you always deep down thought you might get one day, only to realise that the one day never came. As for the friendship ending, it is unreasonable to assume he can be friends with you while married to his wife?
If you guys were only just friends then you could be friends, and you would have been invited to their wedding perhaps, but when you get married (for me anyway) you tell your wife/husband everything and I mean everything about your past and it would make his wife feel uncomfortable knowing he was friends with you given your history. He also probably does not want to get tempted by you and is being faithful.
You have said more here about this man instead of your current boyfriend? How long have you been in a relationship for? I think you need to ask yourself how invested you are in your ongoing relationship and focus on him or if he is not for you then go and find the man who is for you. I think you just have to let life happen naturally and be open to possibilities and your one true love will come along when you least expect it.
I am not saying forget about this man that got away, grief that loss and then move on.