If I Go To A Dermatologist For A Full Skin

If I go to a dermatologist for a full skin exam. Is it ok to request that you do not want to wear a robe? I want the doc to get the full picture and not only see me in sections. but not sure if it is appropriate? I have concerns with my skin on my back, arms, stomach, and penis. Really nervous and feel if I wear a robe they may not get the full picture of why I am concerned. Also I don't want to be labeled a pervert for requesting robe naked without a robe during the exam. How should I proceed.