The fear is common
Almost everyone who returns is sure they carry the one unforgivable sin. They rarely do. The conviction that you are beyond mercy is itself a temptation, not a sentence from God.
Returning
Yes. There is no sin God will not forgive when it is brought to Him with honesty and sorrow. The Church exists for exactly this.
Short Answer
The fear that you are the exception is old, and it is not true. Scripture and the constant teaching of the Church are clear that God's mercy is greater than any sin a person can bring to it. Mercy does not ask you to feel worthy. It asks you to stop hiding and bring the thing into the light, usually through the sacrament of confession.
Almost everyone who returns is sure they carry the one unforgivable sin. They rarely do. The conviction that you are beyond mercy is itself a temptation, not a sentence from God.
You do not have to repair yourself before you come back. Forgiveness is given to the honest and the sorrowful, not the impressive. Confession exists to give what you cannot manufacture on your own.
In confession you say what you did simply and truthfully. You do not need to explain it, excuse it, or relive it. Plain words and real sorrow are enough.
When a priest absolves you, the sin is forgiven. Returning again and again to despair over it is not humility. Accept the mercy and keep walking.
Do not let a screen carry what belongs to prayer, conscience, and real people.
A page can clarify the path. It cannot walk it for you. When a question asks something of your life, bring it back to God, the Church, and the people entrusted to guide you.
Next Steps
Source Trail
Good answers should point back toward sources, not ask you to trust a confident tone.
The bishops' overview of the sacrament where this forgiveness is given.
Open source ↗An examination of conscience to help you prepare honestly, without panic.
Open source ↗The Church's reference for her teaching on sin, mercy, and reconciliation.
Open source ↗Continue