Is this a mortal sin?

I struggle with lust in the heart and impure acts. I always confess to Father those two things but I never add the circumstances to it. I have to know, do I also have to tell Father the circumstances that make it worse? For example, if one suffers from homosexual, extramarital, incest, etc… fantasies, do they have to include that in when they say “lust in the heart”? This has been bugging me for the last two days since I only say “lust in the heart” and since I don’t go describing what type of thing I am lusting after. Have I been taking Communion in a state of mortal sin because I haven’t been describing this sin? I’ve been very nervous of this of late.

Thank you.

Jimmy Akin of Catholic Answers:

As to confessing “lustful thoughts” -as to kinds of “lustful thoughts” - the confessor can guide you -I am not entirely sure at the moment regarding kinds of thoughts- a good confessor can guide one.

While one does* not get all detailed -if something changes the kind *of the sin -that would need to be mentioned (like it would seem to be off the top of my head that if someone had lustful thoughts about a relative -as their relative in particular- that would strike me as something to note but the confessor can guide one.)

Now lets say that a person went to confession and meant to confess all their mortal sins as they ought to be but forgot one or even say called adultery “fornication” by honest mistake -does that mean it was invalid? No. But in the next confession they would confess I forgot such and such or “I confessed fornication but it was really adultery cause they are married”.

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