Almost nothing is more devastating to someone than discovering that their spouse has been unfaithful to them. Not only do they feel rejected and betrayed, but they also find it very difficult to rebuild any trust.
This is one reason God condemns adultery so strongly. God gave marriage to us, and His perfect plan is for a husband and wife to be faithful to each other as long as they both are alive. The Bible warns, "Can a man scoop fire into his lap without his clothes being burned? . So is he who sleeps with another man's wife; no one who touches her will go unpunished" (Proverbs 6:27, 29).
The key to rebuilding trust between you and your husband is to rebuild your marriage–and the key to that is to commit it to God. If you have never done so, ask Christ to come into your lives, and then make Him the center and foundation of your relationship. Learn to pray together ... read the Bible together ... attend church together ... and love God together. Let Christ's love be your example — a love that looks beyond your own needs and desires, and seeks to help and strengthen each other.
This isn't easy; the scars of the past may take time to heal. But when we know Christ, He forgives our past, and He also gives us the capacity to forgive others. Don't give up, but ask God to help you start again. With His help you can.