I will not say you should immediately seek a therapist so that you can get rid of (force them underground) those ideas. Thinking about "bad" things is not doing bad things. All of us have those as possibilities, but they are not certainties, and we can avoid doing things, if not thinking about them. I think exploring obsessive ideas might be a good thing, if you can do it with a sort of "scientific" attitude -- trying to grasp why the thoughts are happening, not immediately condemning yourself for having them. IF you could find a therapist who could gently help you in that exploration it might be a constructive thing, but not all therapists are trained to approach things that way.