You see my brain tells me there is no hell but something else makes me fear it. I guess it's a mental illness of sorts.
Sounds more like a form of anxiety to me. Maybe something you were told as a child, although you don't remember it, could be behind it.
On the other hand I had hell drummed into me by my mother, along with the fact that God was an angry god and so somebody to be feared rather than loved, yet I don't, and never did, believe that hell actually exists.