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So I’d say yes, it was a mortal sin, not because what you did see was genially sinful, but because you were willing to expose yourself to a strong temptation. ...

So, don’t take Communion if you can’t get to Confession before tomorrow, but do make an Act of Contrition and decide what you’re going to do when this type of temptation comes on you again, and it will!

Indirect impurity is mortal
when there is proximate danger of grave sin in the act done, that is,
when the posited act _per se_ or from its nature strongly incites the
agent to sɛҳuąƖ passion, as when one gazes long and fixedly at obscene
pictures, knowing that always or nearly always this arouses impure
emotions. The sin is venial when there is only remote danger of grave
sin. This happens when the posited act is not of a venereal kind (an
unnecessary conversation on indifferent topics) or is only mildly
exciting (e.g., a passing glance at an obscene object), or when the
agent himself is not greatly affected by it (e.g., when an old man, or
one who is of very cold disposition, or an artist whose only thought is
the esthetic excellence, carefully studies a picture of the nude).

Thank you very much for this. So my sin is venial. I will refrain from confess until 1 week has passed. (My confessor has told me not to go to confession more than once per week unless i commit a mortal sin).