The principles of moral law that no one is deemed to be ignorant of are generally those contained in the Ten Commandments. Across cultures those of all religions and of none have recognized the immorality of killing, stealing, lying, and adultery; they have also recognized the importance of honoring parents and setting aside adequate time for rest from ordinary responsibilities. Because these principles seem to be embedded in the moral conscience of man (cf. Rom. 2:15-16), this is why no one is deemed ignorant of the principles of moral law. Indeed, many of the prohibitions of the Ten Commandments are written into civil laws and so those who do not know the moral illegitimacy due to religion would know it due to the civil code.
However, as Paul acknowledges in Romans 2:16 only God can judge hearts and know the culpability for sin of an individual soul. If you broke the civil code, ignorance would not be an excuse because humans cannot read your heart and know your personal level of culpability; but ignorance of the moral law is known to God and he will judge accordingly.
If you were baptized when you entered the Church, all of the sins of your past life and all temporal punishment due them have been wiped away, so you need not worry about them. If you were already baptized and made a sacramental confession of the sins you committed since baptism when you entered the Church, those sins have been forgiven. Try not to let past sins haunt you because those thoughts are really temptations to despair of God’s mercy, love, and forgiveness. God bless.
Understanding Scrupulosity** by Fr. Thomas Santa, C.Ss.R.