Do you know what King David said when he recognized his sin?
Listen to Psalm 51:1-4.
Have mercy on me, O God, because of your unfailing love. Because of your great compassion, blot out the stain of my sins. Wash me clean from my guilt. Purify me from my sin. For I recognize my rebellion; it haunts me day and night. Against you, and you alone, have I sinned; I have done what is evil in your sight.
Is there a hidden sin in your life?
God is merciful, and he WILL forgive... so don't be afraid. Confess it, and ask Him for forgiveness.