You might be showing signs of scrupulosity, but you are still pretty young.
I am very scrupulous and the advice that I have been given in regards to sins you have
unintentionally forgot to confess in your last confession is that they have been forgiven and you do not need to rush back to confession as soon as you remember them. If they are considered to be mortal sins and you just happened to forget through no fault of your own, then mention them in your next confession, but it doesn’t have to be immediate. You are free to go to Communion until then. But, it would probably be good when the opportunity arises to go to confession. Just don’t stress too much on it.
HOWEVER! If you
purposely chose not to mention a known mortal sin in your confession and kept silent with this one, the confession is invalid and you need to go back and reconfess all mortal sins from the invalid confession as well as the sin of willfully withholding a known MORTAL sin in a previous confession. You CANNOT receive Communion until you have made a valid confession, otherwise, you would be adding another sin (sin of sacrilege) if you decide to receive Holy Communion while under mortal sin.
Now, mortal sin needs three requirements for it to be considered a mortal sin.
- Sufficient knowledge
- Grave Matter
- Full consent
If any one of the three are missing, you have not sinned mortally. It may be venial or objectively mortal, but you are not guilty if you didn’t know (unless you willingly chose to not want to know if something was considered sinful, which means you would be guilty of a sin) or didn’t give full consent (partial consent does not make it a mortal sin, but venial).
Scrupulosity is a terrible thing to suffer from, so please do speak with a good, holy and patient priest about this. I strongly recommend you talk to a priest regardless of the advice given on this board. At times, I go to confession three times a week! Only now am I about to seek professional help (I already have a spiritual director). If the priest you will be seeing thinks you are suffering scrupulosity, put an end to it as soon as possible. Even if he recommends you to counseling, don’t be scared or discouraged by that. It would be best for you to do so if it is recommended.
I’ll pray for you. Pray to St. Therese of Lisieux, St. Alphonsus Liguori and St. Ignatius of Loyola as they suffered from scrupulosity.
If you do commit any MORTAL sins since your last confession (venial sins do not require to be confessed in the sacrament of confession but a simply Act of Contrition and sorrow is sufficient for forgiveness and the Eucharist forgives venial sins), please confess those as soon as you can. In the meantime until you can go to confession, make a perfect act of contrition and trust in God’s mercy. Never fall into despair.