The deep issue here is the quote "I can't admit something like this to my instructor".
Why not? The instructor's role is not to berate you for what you don't know, it's to help you become a professional, confident CPL. Pax won't want to fly with you if they sense you aren't sure what you're doing. I know that!
My suggestion, vary your instructor if intimidated, or just sit down for a beer after a day's training and have an honest chat. If they were any good, they would offer a change in training methods, and some specific Nav practice to bring your confidence flooding back.
I found Night VFR navex really sharpened my Day Nav skills. Maybe start giving that a try now...
Matt