You don't sound psychotic at all, at least not in the true meaning of the word. You have a strange sexual fantasy, and nothing more, but the fact that it's worrying you is what is ruining your life. As I have said to others here, you should not feel ashamed of whatever sexual fantasies you have in your head. Provided you understand that - A. They aren't accepted by society in general; and B. They would be best kept inside your head, never to be erxpressed to the wrong person - then you should be able to get on with your life. If you want to improve things, then I believe setting some 'ground rules' with yourself might help, such as you allowing yourself to only view a certain number of images each night, etc. If yuou cannot do this, then it seems that you'll need help in the long term to shake this off.
In my view - and especially in your case - I believe that it should be viewed as an obsession more than a paraphillia. You are obsessed over it in the similar way that a person with OCD would become obsessed over certain thoughts they have in their head. It's fine to disagree with me on this, as I am not a professional in the area of psychology.