What should I do about this

[Bonaventure]

So when I go to confession I confess all the sins I can remember but recently I became aware of the sin of scandal and how it has to be confessed at a circumstance. How should I go back and add them to all my sins from 15 years?

Unless you willfully, intentionally, with 100% full consent of the will withheld a certain mortal sin from confession, you shouldn't worry about it.

How would you confess a sin of impure thought that happens thru the *complete* marital act if you know what I mean. I know pollution is a circumstance that has to be confessed but what about if it happens thru the marital act instead? Do these things matter to the integrity of confession?

I have just been confessing them as "through the complete marital act I entertained thoughts of____" but I see some people just say impure thoughts without saying if they uh *completed* or not

This doesn't make sense to me.

If you are engaging with the marital act with your spouse, you are allowed to have thoughts that you enjoy, want, or crave the pleasures tied with that act. This is normal and it would be weird and even non-human to not have such thoughts and reactions.

"Pollution" is only an issue connected with men. Certain physical responses that women experience during arousal and the marital act are not "pollution."

Unless you are willfully engaging of thoughts of someone other than your spouse during the marital act, which doesn't appear to be the case, I don't think you should be worrying at all.

I am hesitant to go further into detail as this is mixed company and you're very scrupulous.

My opinion there is nothing sinful here at all.

[Bonaventure]

I'm not sure if lustful thoughts during the marital act is venial and not mortal. I haven't found much information on this.

There's no such thing as "lusting" for one's wife, unless one is truly treating her as an object and not as a person.

If the penitent was lusting after someone other than his wife (i.e. "thinking of somebody else",) that's just the sin of entertaining impure thoughts, albeit made more grave by the circumstances.

Yes it wasn't my spouse. And it wasn't regular things I was thinking of so how should a person confess this without causing scandal to the priest

Why on earth would any sin be scandal to the priest?

[Bonaventure]

Did you consent to the thoughts or was it just intrusive thoughts that can happen to anyone, its the difference between indulging the fantasy or having a few seconds thought and then saying, no I don't want this which is not sinful afaik. 

This is a very good question.  People with scrupulosity really need to follow the advice of their confessors about whether to include thoughts in their confessions.

Yep. A thought that flashes through one's mind is not a sin.

You have to have that thought, then willingly choose it. I want this, I like this, I choose to dwell on this.

We cannot accidentally commit mortal sins. Especially of impurity.

As one who has struggled with debilitating scruples at the end of the day, threads like this can only go so far.

You have to find a confessor you trust and listen to him.

All these threads, examens, etc end up doing are feeding the scruples.

Stop posting about it, find a priest, pour your heart out, make your act of contrition, listen to the priest, and trust in God's mercy.