Moral scrupulosity OCD, or the relentless pursuit of certainty about one’s morality, can feel like a truly impossible situation.  You have a thought about something you did or thought about doing, or felt an urge to do, and so forth, and because this experience doesn’t line up with your presumed identity as a moral person, you feel bad.  Because you feel bad, you try to get the feeling to stop. You may seek reassurance, try to make sure you’re not doing bad things, check to see if you have, and engage in other compulsions.  You set up a series of rigid rules that apply only to you to guarantee you’ll never do a bad thing, but since these rules are impossible to follow perfectly, they also make you feel bad. 

What’s worse, ceasing to feel bad makes you feel like you’re getting away with something, like you stopped caring about your moral compass.  Bad feelings at least reminded you that you care and reassure you that you would never intentionally be immoral.  So you find yourself trying to get away from the pain of bad feelings while at the same time clinging to those bad feelings for proof of inherent goodness.  Ultimately, this compulsive relationship to moral doubt sends the message to your brain that thoughts about morality are codes to be cracked, problems to be solved.  So, the brain faithfully performs its duty to help you by sending more intrusive thoughts and feelings your way.