I am not sure this is ocd, exactly. Thought ocd, perhaps? This is when random thoughts stick when most people would let them float out of their head. Then you have a compulsion to prove it or disprove it, whatever the case may be. You research, go through mental thought rituals, seek reassurance, etc. It's not a false memory. That's not really ocd but a stuck thought could be. Anxiety can lead to imagining things (false memory) as well (ocd is a form of anxiety). I will say that it is quite an illness to battle. And often, it's not one subject that gets stuck. You'd likely notice it in other ways. But regardless, things that make it worse is stress and fatigue. The brain just will not cope well if those are bad. That's why night time is awful for ocd thoughts. The brain has worked all day so is tired and can't cope with the thoughts and they take over. The gold standard of care is ERP or exposure response therapy. It's a little tough. It involves NOT doing any compulsion (mental rituals). You float with the thought. You say 'maybe, maybe not' or 'it's just a thought like any other thought' and do nothing with it. If you start to ruminate? Go do some laundry or watch a movie. It IS hard, I'm not going to lie. but about the only way to stop intrusive thoughts. Medication can take the edge off especially when used with therapy.
Have you seen a therapist that specializes in treating OCD? My son saw one and it helped a great deal. Little quirks occasionally pop up, but not the debilitating issues he had before the therapy.