Hi ! …
In regards to your question,
A LOT of posters here will offer their ‘opinion’
And their opinion may not reflect church teaching at all,
And another problem today is that a LOT of priests do not know the Catechism (which they and you are both bound in obedience to),
This is what the church officially teaches:
The Catholic catechism states:
Mortal sins must be mentioned by:
- specifically by name
- by number (or approximate number if unknown)
Deliberately not telling a mortal sin is the mortal sin of sacrelige and renders the whole confession null, which means the whole confession has to be said again, according to the Catechism.
Only you know if you deliberately withheld mortal sins or whether it was an accident.
Confessing the commandment against purity, also means mentioning whether it was:
Adultery, masturbation, fornication, pornography, use of contraceptives, abortion, homosexuality,
sodomy (is the sin you forgot to confess),
All these sins have different levels of gravity against onself, God and neighbour.
Yes it needs to be confessed.
Confessing: an ‘impure sin’/ ‘sexual sin’ is not enough as it could mean ANY of the above.
The Catechism also states:
If you accidentally forgot to confess a mortal sin, all sins are forgiven, but it states you NEED to confess any remembered unconfessed mortal sins in the next confession, because the rule remains that mortal sins must be confessed specifically by name and number (or approximate number if unknown).
The problem today is that you need to double check, did the advice my catholic friend/ priest give me, line up exactly with what the Catechism says).
Priests or laypeople, are not allowed to go agains the official Magistrium of the Church or against the Catechism of the Catholic Church,
If you are unsure if you withheld a mortal sin deliberately or accidentally,
Then have a general confession just in case (which means confessing all mortal sins committed from birth up until now), and then you can rest with a peaceful conscience ️