When we are baptised and filled with the Holy Spirit our spirit is regenerated. In effect, we are crucified with Christ (the old man dies, with original and personal sins) and raised to life in His resurrection (our spirit is recreated). We are grafted into the family of God a new person, now a child of God (no longer to be identified as a “sinner”, although we of course still sin), because of both Christ’s death and resurrection (Romans 6:4).
It is through the blood of Christ that our sins are forgiven - all sins past, present and future have been paid for, regardless of whether you have appropriated that sacrifice in your own life or not. It is by applying the blood through repentance or confession that your sins are forgiven (vatican.va/archive/ccc_css/archive/catechism/p2s2c2a4.htm) - truly wiped away, as if you had never sinned.
There is the matter of our heart and mind, however. Which does not get regenerated at baptism, but which Paul says we must “work out our salvation” (Phil 2:12 - the Greek word which is translated as salvation, is actually wholeness or completeness). This is an ongoing process of dying to oneself, through the Grace and power of the Holy Spirit - so that “it is no longer I that live, but Christ that lives in me” (Gal 2:20).
This is something beyond just repenting of sin and involves a process of purification, of which the Lord works actively on your behalf to help you say yes to His working and then gives you the Grace to perform it (Phil 2:13).
My suggestion is to focus on loving Jesus through prayer and praise (like singing songs to Him) and regularly go to confession (like maybe once a month if there is nothing serious). “Love covers many sins” and so if you focus on loving Him and discovering His amazing love for you, you will be less inclined to sin and your confession will be perfect (as noted in the catechism link above, item 1492).
Blessings
