False Guilt
When the enemy tries to bring guilty feelings (Satan is the accuser Rev 12:10) there are at least three good ways to do battle. It would probably be a good idea for you to put these on an index card so you will have them at hand when you need them.
1. Remind yourself and the enemy out loud if possible that you have been forgiven and cleansed based on 1 John 1:9. God does not recognize that sin any longer and you choose to line your thinking up with God's.
2. Every time the enemy reminds you of it, use it as a reminder to verbally thank God for forgiving you.
3. If you are still tormented by those thoughts use it as an opportunity to verbally remind the enemy that Jesus Christ won the victory over sin that he is defeated and you have chosen the Lord's side. That God knows every detail of your life and He loves you very much Ps 139.
The enemy hates to hear these things and if you use his torments as a signal to affirm these truths it usually sends him scurrying. After a few tries he will likely give up on trying to bring this torment because you are using it as a reminder to worship God for His goodness to you.