@Alwaysonmymind,
Unburdening your guilt is a selfish motivation for telling your husband and more than likely connected to a hope that it will end the marriage that you don't have the courage to end.
Make up your mind (although I think you have). If you no longer want to be married then tell your husband in a way that minimizes his pain.
If you do, then keep your mouth shut, live with your guilt and work to make things right.