I don’t really have an answer to the question in the OP, but,
If you are having compulsive thoughts that ‘X might be a sin!!’ etc. I would not say you are necessarily sinning every time you do something that you have scrupulous suggestions telling you may be sinful. What you should do is mention this and explain your situation to a confessor who ideally you would see regularly, and follow his advice.
Anyway, under normal circumstances, I think this kind of sin by ‘willingness to sin’ is usually still specific in kind: a sin committed by defying the conscience would be whatever kind the conscience was convinced was or might have been being committed. So if I were convinced in conscience that it is a mortal sin to eat meat on Wednesday (say I was incorrectly taught that growing up), and had no reason to doubt it, if I do so anyway my act of the will (i.e. sin) was to disobey the Church’s precept in a grave matter even though my external action was not so.
Again under normal circumstances, when there is doubt the appropriate action is to resolve the doubt before acting. With severe scrupulosity, though, the doubt is multiplied and spread out, and without 1) help from one’s confessor (i.e. following his guidance) and 2) possibly medical help or therapy for potential OCD, managing the doubt can be practically impossible.
Of course as you have recognized, the conscience is supposed to be our guide that we are to always obey. But as in your case you are aware that you have issues with scrupulosity, it would not be appropriate to live in doubt and fear, avoiding everything your mind suggests might be a sin. You should seek guidance from one confessor and follow his advice.
However, in my case I’m able to provide some “reasons” to support this thought.
I wouldn’t say this is uncommon. Sometimes a tenuous but seemingly very real connection can be made between a certain action and grave sin. It’s something that, and I know I’ve said this multiple times here already, you should get help from a confessor with.
I think with scrupulosity as it deals with sin it can get tricky to know what to trust and what to ignore. I have OCD, and on matters related to certain things I know exactly which thoughts I should ignore. When the stakes are high like with sin though, it seems obvious why one would not want to risk defying these suggestions of the mind because of the whole conscience thing. Generally, I would think a conscience which one knows to likely be in error should be
informed (by one’s confessor) rather than strictly obeyed or defied.
