years ago, i struggled with similar things, not feeling like i was real or the world around me was and having thoughts that were very confusing. at one point, a medication i was on made it so bad i thought that i had to try to harm myself in order to find out if i was alive or not and caused my dissociation to get so much worse until i went off of it.

i also struggled with intrusive thoughts/images/fantasies. i thought that i was crazy, and they really bothered me. i had them for several years and talked to a professional once about some of them who assured me i was not dangerous. there were recommendations to help me though. but i believe for me, they were a mix of OCD and anxiety, trauma, and dissociation. they did eventually lessen and completely stop...but it also came from me growing, time, etc.

i would suggest talking to a professional about it though so they can help you sort things out. if you feel like the thoughts/fantasies/images cause anxiety and fear, it's more likely you won't act on them..but it's still better to talk to a professional who can explain what it may be and how to get through it safe.