I've had similar thoughts as well. For me, it was a stress and hormone trigger.. After I had two of my four kids, I had those intrusive thoughts really bad. Fortunately they subsided. Someone told me, that even though they can be very disturbing, the most effective way of getting rid of them, is to actually let the thought play out in your head without trying to stop it. It actually did help for me. The harder you fight the thought, the harder it is to keep it out.