IF YOU WANT YOUR MARRIAGE:
First, you must be strong enough to stand for your marriage. The key is to ask God for more of His grace. Ask the lord to shield your heart and ask the Lord to love on you more. It's best to get your love from the one true love, God, and not something/someone else. Ask for strength to get through this season. Just know that there is victory at the end! Pray for your spouse as your brother, not husband. Deception may have the best of him now, but God will reveal and deal with your husband in His timing. Fast if the Lord is leading you to do so. This is a spiritual fight and you need to be sensitive to the voice of the Lord. If He says, praise, then praise, if He says fast, then turn down your plate, if He says pray in tongues, anoint your husband's shoes etc, then be obedient and do it!
Some husbands may want you to agree with his extra marital affair. There are even some wives who may even 'find' a woman for their husband's fetish and be okay with it. These wives mentality are, "I rather know who he's doing it with and know she is ......" I recall one relative of mine putting condoms in her husband's suitcase every time he would go away on a business or R&R trip. She said that she rather for him to be safe and not bring a disease home to her. Either way, it's still wrong and not pleasing in the eyes of the Lord. Do not condone this behavior in anyway. Stand for truth and righteousness.