First and foremost, you are able to pray to God about your mistakes. Confession is the means Jesus gave us to make full contrition for our sins.
Many times Christians struggle to know what must be confessed in the Sacrament. This is good, but I believe the answer always comes down to you and God, in the end. What I mean, is that you know what was an offense to God, and your relationship with Him. He gave us a conscience, which we must strive to keep pure. This means Confessing what bothers the Holy Spirit. When we try to form our conscience, we should be seeking what is pleasing to the Lord, instead of merely wondering what He is gonna punish us for.
The only time I avoid Comminion is when I am struggling to regret something. When we are truly remorsefull, and intend in our hearts to be Reconciled, we are strengthened by His Body and Blood.
Please do not be so embarrassed about this that you keep it from Jesus. Telling our Priest in Confession is the holy sign that you are truly bringing it before Jesus, and not keeping it a secret. When our hearts are truly remorseful for committing sins, we will then committ Confession ;). I doubt anyone regretted confessing anything they thought may have been an offense to Jesus.
Do not dwell on this mistake too much. When you have Confessed, forget about it and never return.
Welcome to the forum, if you plan to inquire more. Pray for your pastor and parish helpers