Something weird happened to me where my head went mad for a good few months and it was really scary.
First I thought I'd done something evil and couldn't remember, took over all my thoughts trying to remember.
Then went batshit-
Thought I must have multiple personality disorder and not know it l, thought I was a psychopath. I thought I killed someone! I didn't obviously but at the time I thought I did and just couldn't remember and kept getting fake memories/flashback type things.
Thought the police were spying on me, hacking my phone. I even saw a message on my phone "from the police" because obviously they text the people they're spying on 
I thought they were following me/stalking me.
I thought my boyfriend was trying to poison me because I'm so evil that he wants to kill me. I couldn't do ANYTHING other than shower and chain smoke. Couldn't eat.
It sounds mad now and it eventually went away on its own but I'm going to the GP soon probably to help make it not happen again hut just want some thoughts maybe on what this could be so I'm a bit more informed when talking to the Dr, don't want to be fobbed off or anything