I've had obsessive thoughts that were similar in nature, but different in what I thought about. It's not entirely irrational from a philosophical perspective. I think, if you relax a little bit to make your train of thought clearer, writing about your concerns & beliefs will make you feel better. You could just be having a spiritual crisis, where you are questioning your place in the universe. Not every irrational thought is a matter of mental illness-- Sometimes our mortal curiosities sneak up on us at the most inconvenient times.

Good luck on feeling normal soon!!