Thanks, from the definitions you've given it sounds less like intrusive thoughts or anything OCD related, and more like delusions. But I wasn't sure if they could be considered delusions because I can consider the possibility that what I believe isn't true, even though I still somehow do completely believe that they are true. I don't really know tbh.
It was just that certain things I experience seem more like intrusive thoughts. Like one time I suddenly started seeing scary images in my thoughts, but it didn't feel like something I would think of or could imagine normally. I don't know how to explain it, but the images were completely different and unusual, and I felt sure that they had been "placed" in my head. It's only happened a few times though, so it's not much of a concern right now.
(Would this be better maybe to discuss in the Schizophrenia and psychosis forum then here?)