Paul wrote about this very issue in Romas 7:15-25. He struggled with sin...as we all do. He even noted that the good he wanted to do, he did not do it; rather he practiced the evil he did not want to do.
By your thinking Paul had lost his salvation. And if I'm reading your post correctly, there was no loner any hope of regaining salvation.
Paul goes on to write the following in Romans 7:24-8:2 wretched man that I am! Who will set me free from the body of this death? Thanks be to God through Jesus Christ our Lord! So then, on one hand I myself with my mind am serving the law of God, but on the other, with my flesh the law of sin. There is therefore now no condemnation for those who are in Christ Jesus. For the law of the Spirit of life in Christ Jesus has set you free from the law of sin and of death.
The sacrifice Jesus made on the cross covers ALL of our sins.....past, present and future. He has paid the price for our sins.
Colosssians 2:13-14 tells us He has cancelled out our sin debt and has nailed it to the cross. Our sins are cancelled out. The Greek word used for cancelled indicates they are blotted out....removed.....gone. This is echoed in Romans 4:7-8.
Jesus has forgiven ALL of your sins if you believe in Him.
No sense in disgusting this any future. Go ahead and sin all you want, never set foot in a church, never pray, deny God, because you’re still going to heaven because you were “saved” when you were 20. Lord, help us.