I, too, have suffered from mild to moderate scrupulosity since converting to Catholicism. However, I think a few points might be helpful to clarify.
There’s different types of scrupulosity that can affect a person. The actual concept of “scrupulosity” simply means not being able to tell whether an act is sinful or not, and the torture that goes along with the doubt of the mercy of God. When I was Mormon, I also suffered from scrupulosity. I often was convinced that I was not going to go to heaven (Celestial Kingdom) because I forgot to repent for something quite small in the bigger scheme of things, such as drinking a glass of tea.
Some people suffer a form of scrupulosity that makes them believe, say, that if they accidentally ingested some lipstick before Mass that they broke their fast and would be ineligible to receive. Others have a form where they believe that they must repeat a prayer over and over again until it is “perfect” in motivation, or words, or inflection, or “feeling”. Others, like me, are tormented with unwanted thoughts and have a distinct problem being able to tell if these repetitive thoughts are in fact encouraged or welcomed due to the fact that they are so frequent.
The most significant step that has helped me with my scruples is to come into a relationship with a confessor that understands scrupulosity and who is willing to teach me the steps to reign in those scrupulous tendencies. My confessor has bound me to what he calls “The Rule” - if in good conscience I cannot put my hand on a bible and swear that a certain action or thought is sin, it is not a sin. If I know that it is a sin, but can’t put my hand on a bible and swear that it is a mortal sin (i.e. that I deliberately looked at God and said, “I know your will, but I choose to turn away from it”), then it is a venial sin. Instead of getting in a cycle of examining my conscience constantly, I simply use this rule to evaluate each questionable action as it happens. Now, because I have formed a specific and consensual relationship with my confessor, he has bound me to this rule with the understanding that if I use this rule and cannot tell if something is a sin or not, it is not a sin and the confessor is held responsible for the action and I am not to worry about it any more after that point. I have to have full trust and obedience in my confessor for this to work. As he says, “he’s a professional, he does this for a living.”
I also have an amazing spiritual director who has given me a couple of very concrete steps that stop my scruples in their tracks. For example, to stop that loop of repetitive and negative thought by simply saying, “No, I am not going to think about that.” and then saying a simple prayer of spiritual communion “Jesus, come into my heart” and taking 5-10 seconds to put myself in the presence of God in simple meditation. Sometimes, when the thoughts come in wave after wave, I may do this a dozen or more times in a single hour. But taking that action to stop the thought cycle and redirect my thought energies towards God makes a HUGE difference in being able to stop the mental cycle of scrupulosity.
Reading St. Francis de Sales lately has helped me realize that many of the issues I have suffered with in my scrupulosity are not only common, but very much not sinful at all. Let me give you an example from “Introduction to Devout Life” (emphasis mine):
Picture to yourself a young princess beloved of her husband, to whom some evil wretch should send a messenger to tempt her to infidelity. First, the messenger would bring forth his propositions. Secondly, the princess would either accept or reject the overtures. Thirdly, she would consent to them or refuse them. Even so, when Satan, the world, and the flesh look upon a soul espoused to the Son of God, they set temptations and suggestions before that soul, whereby—1. Sin is proposed to it. 2. Which proposals are either pleasing or displeasing to the soul. 3. The soul either consents, or rejects them. In other words, the three downward steps of temptation, delectation, and consent. And although the three steps may not always be so clearly defined as in this illustration, they are to be plainly traced in all great and serious sins.
If we should undergo the temptation to every sin whatsoever during our whole life, that would not damage us in the Sight of God’s Majesty, provided we took no pleasure in it, and did not consent to it; and that because in temptation we do not act, we only suffer, and inasmuch as we take no delight in it, we can be liable to no blame. … Be then very courageous amid temptation, and never imagine yourself conquered so long as it is displeasing to you, ever bearing in mind the difference between experiencing and consenting to temptation,that whereas they may be experienced while most displeasing to us, we can never consent to them without taking pleasure in them, inasmuch as pleasure felt in a temptation is usually the first step towards consent. So let the enemies of our salvation spread as many snares and wiles in our way as they will, let them besiege the door of our heart perpetually, let them ply us with endless proposals to sin,—**so long as we abide in our firm resolution to take no pleasure therein, we cannot offend God **.
As with all advice, YMMV, and I would
highly recommend finding a confessor who is trained in dealing with a scrupulous nature and working with him to help to tame your scruples if you do suffer from them. The peace I have found from helping to control my scruples has helped me take a very valuable step in my spiritual life.