I am glad your reading the Catechism, its one of the best ways to study the bible. Keep reading. I think your misunderstanding the biblical stance here though. Christ died for all your sins and the whole worlds and paid the price by his cross and resurrection and ascension. The graces that He won for us and enter us into this sacrifice are given in time and space through His gifts of faith, the sacraments of baptism, eucharist etc. Baptism iniitally saves you and washes away all sins you had up till that point(Ezekiel 36:25-26, Act 2:38-39, Act 22:16, Titus 3:5-7, 1 Peter 3:19-21).
But what happens when a person sins or falls into sin after he has been baptized? Jesus is clear that we need to repent and confess our sins to be forgiven after that. That is another sacrament.
"if we say we have no sin, we deceive ourselves, and the truth is not in us. If we confess our sins, he is faithful and just, and will forgive our sins and cleanse us from all unrighteousness. (1 Jn 1:8-9).
This is also why Jesus tells us we need to pray the Our father which ask God to "forgive us our trespasses", and also why Jesus gave his apostle the power to forgive sins and hear confession sacramentally(Jn 20:21-23)