What is the fear of harming others even though you wouldn't ever?

This is going to be hard to explain. Ever since I was little, I've had this fear that I'm going to do some sort of horrible thing to harm something/someone, even though I would never do that thing. It's bad enough that I really don't trust myself sometimes. For example, [this is the only one that comes to mind right now] when I first got my cat when she was just a kitten back when I was maybe 11 or 12, I couldn't look at her without being afraid that I was going to [and i know this sounds insane XD bear with me] put her entire apple-sized head into my mouth and crush it. I was so terrified I'd do that even though i love her and I love animals and i would NEVER, /EVER/ do anything to harm one. I was so afraid I would brutally murder her X'D the worries subsided after a few years when her head got too big for me to be able to fit in my mouth anyhow. but what on earth is this, and is it some sort of disorder? Any tips are appreciated! <3