Is it possible for a single specific thought related to your theme to bother you for a long time

So I had a panic attack a while ago to “kill mom” and I forgot about the thought until a few days later. When it came back I was mentally drained and it lasted for 2 months or more. It eventually went away but it is back. I get other intrusive thoughts but they go away after a hour or so. Why am I stressing over “kill mom” so much. I just get irritated that it won’t go away. I’m beginning to think it’s a different mental illness maybe just anxiety? I’m not sure to be honest. It just appears and sits there and I feel like I’m doomed and a pyscho and worry that I’ll never forget the thought.

Why is it that you beat one OCD think, but another OCD thing comes up related to it, but the same theme?

I’ve had different themes of ocd throughout my life. Can they all differ such as how the thoughts may present? Currently my thoughts feel so true immediately (like they genuinely feel like what I think) but in the last theme I feel like it may have been more of a “what if I think this” type of situation