Or maybe they have to knock 3 times before they do something?
What about the constant fear that they might kill a loved one? That they might make God angry? That they don’t really love their significant other?
This may sound like psychosis but it is simply a defect in the brain’s filter. All people have random thoughts but people with OCD grab onto a thought and think “Is this true? Do I want to do that? Why am I thinking that? Am I going to do it? Why would I want to do that?”
A person with OCD does not want to act on their thoughts, they find them terrifying, disgusting and disturbing. They know that their thoughts are irrational, but the Fear is so strong. The person thinks: “What If?”
They may develop rituals(compulsions) to quell the anxiety. If they are obsessed with germs, the compulsion may be to wash their hands. If they have Scrupulosity, they may constantly go to confession.
OCD is treated with Cognitive Behavior Therapy and various medications. OCD is a strong and resistant anxiety disorder; but once you put effort into recognizing your obsessions for what they are, and maybe find the right medicine; the outlook is very good.