I was baptized Catholic as an infant, but not raised in it. I never heard about venial/mortal sins until I began exploring Catholicism in my late teens. I thought sin was sin.
I understand in Confession, mortal and venial sins can be confessed, but the venial are forgiven during a part of the Mass.
There are a few things in the past that I have done that had I been Catholic and fully aware they were mortal and not just sin, I would confess without hesitation. Like, when dating my now husband, I kissed another guy playing truth or dare while drinking. Or, I practiced paganism for a little when exploring different religions.
I don’t want to be scrupulous, but I don’t know if those need to be confessed or not.
Would you just confess them and tell the priest you didn’t know at the time?
It may be helpful to confess your less serious sins, but not strictly necessary, because they do not constitute a lack of charity towards God or others. The serious sins are important to confess. How can you know if you have any?
The Catechism has some help:
1860 Unintentional ignorance can diminish or even remove the imputability of a grave offense. But no one is deemed to be ignorant of the principles of the moral law, which are written in the conscience of every man. The promptings of feelings and passions can also diminish the voluntary and free character of the offense, as can external pressures or pathological disorders. Sin committed through malice, by deliberate choice of evil, is the gravest.
1859 Mortal sin requires
full knowledge and
complete consent. It presupposes knowledge of the sinful character of the act, of its opposition to God’s law. It also implies a consent sufficiently deliberate to be a personal choice. Feigned ignorance and hardness of heart133 do not diminish, but rather increase, the voluntary character of a sin.
1853 Sins can be distinguished according to their objects, as can every human act; or according to the virtues they oppose, by excess or defect; or according to the commandments they violate. They can also be classed according to whether they concern God, neighbor, or oneself; they can be divided into spiritual and carnal sins, or again as sins in thought, word, deed, or omission. The root of sin is in the heart of man, in his free will, according to the teaching of the Lord: "For out of the heart come evil thoughts, murder, adultery, fornication, theft, false witness, slander. These are what defile a man."128 But in the heart also resides charity, the source of the good and pure works, which sin wounds.
1857 For a *sin *to be
mortal, three conditions must together be met: "Mortal sin is sin whose object is grave matter and which is also committed with full knowledge and deliberate consent."131
1858 Grave matter is specified by the Ten Commandments, corresponding to the answer of Jesus to the rich young man: "Do not kill, Do not commit adultery, Do not steal, Do not bear false witness, Do not defraud, Honor your father and your mother."132 The gravity of sins is more or less great: murder is graver than theft. One must also take into account who is wronged: violence against parents is in itself graver than violence against a stranger.
vatican.va/archive/ccc_css/archive/catechism/p3s1c1a8.htm