Someone could ask, “Where does it say we have to go to a priest?” The first place is in the Gospel of Matthew. Jesus is speaking to his disciples (as seen at the beginning of chapter 18) and he says to them:
Amen, I say to you, whatever you bind on earth shall be bound in heaven, and whatever you loose on earth shall be loosed in heaven. -Mt. 18:18
Now, this is not to say that if one is really sorry for their sins, and can’t find a priest that they’re damned. God is just. He is also life. Sin on the other hand is ugly. It is death (see 1Jn. 5:16-17). It is like a cancer. Cancer, if left to itself, will kill you. Now, if you had cancer, would you only pray to God? Probably not. You would ordinarily go to a doctor. The doctor would prescribe something for you or do something to make you healthy again. You go to the doctor because he has knowledge about and has been given a gift from God that enables him to help make people healthy. Well, priests are doctors of souls. By their ordinations, they have been given a gift from God to be able to forgive sins and make souls healthy. Can God miraculously cure people from cancer? Yes, but God likes to work through the ordinary because God likes order. Just as doctors are God’s ordinary instruments to bring people back to physical health, so priests are God’s ordinary instruments in bringing people back to spiritual health. A perfect example of this is found in James 5:14-15:
Is anyone among you sick? He should summon the presbyters [is the Greek word which we derive the word priest from in English] of the Church, and they should pray over him and anoint [him] with oil in the name of the Lord and the prayer of faith will save the sick person, and the Lord will raise him up. If he has committed any sins, he will be forgiven.
Note that this priest has the power to heal and forgive sins. St. Paul notes this power to forgive and reconcile people to God was given to him as Christ’s ambassador (priest):
And all this is from God, who has reconciled us to himself through Christ and has given us the ministry of reconciliation, namely that God was reconciling the world to himself in Christ, not counting their trespasses against them and entrusting to us the message of reconciliation. So we are ambassadors for Christ, as if God were appealing through us.-2Cor. 5:18-20
So we see that confessing our sins to a priest is in Scripture. We also see that the reason we confess our sins to a priest is not in opposition to Christ, but precisely because of Christ. Through Baptism and ordination to the priesthood, the priest truly can by the grace of God, act in the person of Christ and loose/absolve someone's sins. This is taught not only in Scripture by James and Paul, but by Christ. This is why the Church teaches it. This is why Catholics believe it. This is why Catholics hold it as truth. I pray this helps clear up some misconceptions. May these truths help to continue to bring us to grow in Christ and become the saints God is calling us to be. Praise be Jesus Christ!