I call what you've described, dwodz880, "intrusive thoughts". I believe such thoughts, when they are in excess and disturb your normal life, are symptomatic of an anxiety disorder and are sometimes an aspect of OCD. I have battled with such intrusive thoughts all of my life, as many people do. Sometimes the thoughts are about hurting something or someone I love very much, even though I know I wouldn't really hurt them. It's as though my mind is overcompensating for the strong feeling of love by threatening me...as if my mind is saying, "You're going to hurt or kill that someone you love so much."

Intrusive thoughts are miserable to experience. There are a number of ways to deal with such thoughts. Sometimes medications help, sometimes therapy helps, and so on. I found this page - don't know who the guy is, but the page is helpful. And there is a ton of info online about how to cope with intrusive thoughts if you Google the question.
Martin N. Seif, PH.D. Clinical Psychologist Anxiety Disorders Treatment - Resources