"what if" "what if" its like the OCD theme song, what if this, what if that, no matter how illogical it sounds we just can't shake those thoughts that get stuck in our mind. For each of us its different things, but what you are describing is pretty much OCD sounding to me.
The best thing you can do is to stop trying to debate/argue with yourself about your worries. Ok, easier said than done

But really thats what you will work on if you go through Cognative/Behavioral therapy. Just try and note that you are having the thought, note that its your OCD, and thats it. Just go onwith whatever you are doing, dwelling on your thought, trying to out logic your thought, it only keeps that thought on your mind (ironic isn't it).
If you can talk to a therapist or psychiatrist who specializes in anxiety/OCD disorders so you can get treatment to help you manage your OCD. Trust me it can get aLOT better.