It can happen to anyone and normally its because both your life and your husbands life got so busy with the children and work that you live from day to day and all of a sudden you met this person and he excites you. Please don't think of contacting this person again because he is not interested in you and by contacting him you will just make a fool out of yourself. What is it that excited you about this guy. Ask your husband to do the same or be bold and do something with your husband that you would have loved to do with this guy
It's all a fantasy. He is unattainable and thus safe for you to have this attraction too. It's like having a crush on Brad Pitt (or whoever). It's not real. Think back and remember why you fell in love with your husband. Try and reconnect with him. You probably miss that romance that you experience at the beginning of a relationship. Try to find something with your husband to rekindle it with him.
You need to stop all this foolishness. You made a commitment to your husband. Think hard about what you are doing. This is probably something that you will regret the rest of your life. Good thing he refused to be your lover. Why would you want to break up two marriages? It boils down to selfishness. Think about your children and their father. I can bet that since this has been going on that your relationship with your husband has not gone too well. Get a grip before it's too late.
It is because you are being selfish and lustful. You took vows and apparently do not take them seriously. You should inform your husband that you are not happy and wish to be with someone else. Give him the kids, house and dod (if any) and allow him to find a woman who will love and cherish him unconditionally and be faithful. You are suppose to have eyes only for your husband. It is a personal choice to let the heart wonder and to be lustful. Yes you are wrong but it is your choice. Let your poor husband know and make arrangements for him in the kids so you can go and play. Because playing with a mates heart is not fair. Don't be ashamed of breaking up a happy home. Selfish people do it all the time. I hope he has it in his heart to forgive you and not take it out on the next women.