What if you are obsessed with demons should you tell?

If the obsession is causing you enough unhappiness that you are asking the question, you would probably be happier if you shared the burden with someone you can trust. I would suggest a clergyman, counselor, or trusted teacher rather then simply a friend. They are better-equipped to support you without feeding into your concerns or, on the other hand, dissing them.

Any obsession is a terrific burden for the person who has it, and it deserves serious consideration. It is well to seek that where it is most likely to be found.