What if I didnt know I committed a mortal sin?

[Ranulfus]

I just found out I committed some without knowledge,
Would they be considered a mortal or a venial?

Because it lacks the factor of me not knowing it is a mortal sin.

 

[Hereiam]

At the time you committed a grave act, if you did not have knowledge it was a sinful act you have not committed a mortal sin.

However, if later–even well after the act–you gained the understanding giving you knowledge you had committed a mortal sin, you need to seek absolution for it.

Seek the Sacrament of Reconciliation, confess the sin, be absolved, display contrition, and do your penance.

In an old formula of confession, people used to close with asking for forgiveness for “this and all other sins I have committed.” Perhaps that is enough.

Ask your priest, as you will probably get several different answers here.