I had sex with my husband's best friend

On the eve of our wedding, I had sexual intercourse with my husband’s best friend who was also his best man. I was intoxicated at the time and only realised what I had done when it was all over. Nobody else knows about this but every day I feel so bad because my husband helps him a lot including lending him money often, and even helping him secure a well-paying job. I am now married, yet he is still hitting on me and wants to continue with that. What do I do?

{Lillian}