In a very real sense, repentance requires regret. If, once you stop having sex, you actually regret using contraception, then of course all will be forgiven. If not, then (in a real sense) you aren’t repenting at all. What’s more, committing a sin with the intention of confessing it later adds another sin: the sin of presuming on God’s mercy. Saying “I’ll insult God and then just confess it later” is itself a gravely evil act that requires Sacramental confession. And you must sincerely regret this second sin, too, for your repentance to be genuine.
That said, I don’t think you realize your position here. You say that you know using contraception is a sin. Am I correct in concluding that you know the Church teaches that using contraception is always grave matter, and you agree with that position? You aren’t dissenting from the Church’s position, you are saying that you will knowingly and intentionally commit a gravely evil act?
The entire Christian life cries out against that position. You’re knowingly and intentionally consigning your immortal soul to hell if you should happen to die in the next 40 years. You’re knowingly and intentionally committing an act so contrary to the nature of the all-loving God that his sanctifying grace will be unable to reach you at all. You’re knowingly and intentionally saying to the God who created you, was tortured for you, and died for you, “I don’t give a damn about the moral law that exists for my greater happiness and sanctity. I don’t give a damn about being with you for all eternity. I don’t give a damn about your design of human sexuality to image your own life-giving love. I care about my sexual freedom more.”
Do you see how utterly contrary to everything Christian the position you’ve staked out is? You say that you know and believe that contraception is immoral. Don’t do this, my brother in Christ, I beg you.
