Put yourself in his shoes. If he cheated on you, would you want to know? the answer is most likely yes. Although it will not be easy-and could possibly destroy your relationship-you owe it to him to tell him. Additionally, you probably need either some serious marriage counseling or to leave.
It can be considered selfish to tell your husband out of guilt. If you truly feel remorse for what you have done, you should learn from your mistake and resolve in your heart you will never do it again. I've made the mistake myself, you can use this to make your relationship stronger. You can be stronger too with how you deal with this.
