when people tell me that they have a guilty "conscious" it is usually because they feel guilty about something.  You may not think it's relevant to the polygraph exam, but you appear to be witholding something that you feel guilty about.  Just let your examiner know what you are thinking about when you hear those questions you mentioned, and you will be fine.  Most of the time the examiner isn't really concerned with information you provide, only that you provided everything.