When should you tell your spouse that your are having an affair with someone else and you are in love with this person and you feel that your lover can and will fulfill your life with happiness?
Well first I just gotta say that you should have discussed the problems in your relationship with your spouse and maybe got some counseling, but seeing as you didnt and you have moved on you should tell your spouse now, there is never a good time to tell the person that you promised to be faithful and honest with til death do you part that you have cheated on them and no longer wish to be with them. It is unfair of you to keep dragging your spouse on, and let them live the lie you would call marriage.
I'd forget about telling him just now, and take the rose-colored glasses off and reread the marriage vows you made to your spouse when you believed THEY were the one who would fulfill your life and bring you happiness. Truth is that no one person will do this and it is unfair to expect anyone to...certainly working at happiness is a two way road, and cheating is not one of the roads that lead to it. I'd try to realize the pain this will cause all around. Although you will need to tell him at some point, preferably talk with a counselor who would work to preserve the marriage and even to restore it. Yes, it is possible even if it doesn't seem like a very exciting way. The counselor may be able to advise the best way to break the news. This is, after all, news that is going to tear another person's heart out and great care needs to be taken. The worst thing to do now would be to let things continue in deception as mentioned by the first answerer. I'd fix the underlying problems or they will recur in the future.