What to say when you honestly dont remember?

[zxcmnb9001]

Hi all,

I am a new member to this forum and am grateful that this site exists.  I have a few disconcerting questions regarding an upcoming polygraph for entrance into a local police academy.  I have been unofficially (by neurologist) diagnosed with OCD (thought based, not physical manifestations) and I have extremely rare cases where I form an obsession and compulsion to a particular bothersome thought.  This leads me to my question.  I have a particular question that I know will be asked of me that I have formed an obsession and compulsion too and it has caused me to not be able to remember it (even though im 99% sure I didnt do it and 100% I would never do it...if that makes sense).  I try to recreate the thought in attempts to remember it away but I cant.  This is very bothersome to me and I wonder if I should take my chances and explain this, contrary to it sounding like a blatant lie, or should I just say no and hope for the best? Or ask if they could word the question so that I could answer yes or no regarding me "not knowing"?  Your thoughts?

Thank you so much in advance!