I'm sorry to disagree with anyone on this site but I do think you absolutely MUST tell your husband about your affair. The guilt will eat away at you and you will be keeping a secret from him as long as you live! How can you do this to the man that is supposed to be completely intimate with you? Please see the info on honesty in marriage on the site:
www.Marriagebuilders.com They stress complete honesty as the only way to fly. I agree!
The thing is, your husband is already suspicious. Do you want him writhing in torment wondering the rest of his life? He already does not trust you like he should and the longer you wait to tell him, the worse it will be for him. please do not let one more day pass without telling him or writing him of your wrong. He can get over it if he will remember that you really do love him and just made a big mistake. But if he can't get over it, well, that is something you have to face. If his love for you is not enough to get over a sin then how much does he love you?
The next thing you must do after confession is to be completely accountable to him. Tell him how you intend to let him know where you will be and with whom you will be every minute of every day until he feels he can trust you again. Tell him to check up on you, to spy on you, to do whatever he needs to do to feel safe again. But don't just rely on him to check on you--let him know yourself! You owe him that! Do not let him talk you out of it either. Call him regularly if you can, to tell him you love him, are thinking of him and then, when you going to be away from him, tell him where you will be and how long and every single time you are going to be longer than you said you would be, call him and tell him why you will be late and when you will be home.
Your 'sentence' for being untrustworthy is to be completely accountable. it doesn't matter how childish it may seem to you, you are having to build trust in him from the basement floor. And it ain't easy! He needs to KNOW (not trust--trust is gone) that you can be trustworthy. How can he know you can be trusted unless you prove it to him? And you must continue to prove it over and over and over until he is satisfied. That is the only way you can have trust back. Tell him you are going to prove you can be trusted and then PROVE it. Prove it by having an open life--he should know where you are, whom you are with, how long you're going to be every minute of every day! That is not too much to ask of you for his peace of mind.
And then never ever be alone with another man in any place for any length of time. Don't strike up friendships with other men, don't go to lunch with a business associate alone, never dress in any kind of immodest or provocative clothing, don't write to other men, don't even talk to them if you can avoid it for awhile--do NOTHING that would make your husband uncomfortable or jealous. In fact, go overboard in that area!
Trust is as delicate as a butterfly's wing--once broken it is as difficult to put back together as that broken wing. But it can be done! LOVE is the answer. And, as the Bible says, Love covers a multitude of evil.