Hi Celestial -
Welcome to one of the most common dreams of all - being naked or partially attired in public - with a twist; no one seems to notice that you are naked!
Dreams of being naked in public typically reflect feelings of unpreparedness - or fear of exposure. In your case, because the dreams almost always take place in the setting of being “back in school” - and because school is a location where our knowledge of various subjects frequently is tested - your dreams most likely are related to doubts about your abilities - in either your personal or professional life.
It is significant that your dreams started two years ago. To figure out what arena of your life you feel “unprepared for” or “vulnerable to exposure” - think back to what major event occurred two years ago that seems related to the dream. For example, maybe you changed jobs and suddenly felt you had to “bluff” your way through some of your new job assignments - and you were concerned that your co-workers would “see through” you. Or perhaps you became single again and suddenly were worried about your ability to raise kids as a single mom. In a classic “fear of exposure” scenario, perhaps you had an affair or committed some other act that you still dread others learning of.
What is interesting about your dream is that no one else seems to notice your nakedness. This suggests that you are overly concerned about whatever vulnerability it is that you are feeling. In this regard, your dream is encouraging you to relax and lighten up a bit. (No one else notices!)
I suspect that with a little bit of work you will be able to fairly easily identify what change in your life caused this new-found sense of vulnerability. Are you willing to ...expose yourself... and share the answer with the rest of the world? :-) If so, write back and solve the mystery!