Been there, done that,.
Such good answers above, I just threw a mother of all temper tantrums, lol.
It was one of the first things my Husband had set out to "destroy" within me - my sense of propriety and embarrassment - to make it clear that there would no such barriers between us.
Care to guess what method He choose to accomplish that?
If you answered, ordering me to strip and masturbate in front of Him whenever it hit His fancy, get yourself a brownie.
To answer your original question, asking for a time out or asking to talk about it with him (some time) after session might be helpful. Ask Him what purpose it serves, what it is he is trying to accomplish? Tell him how hard you find it to do, then talk about why. Ask him if he would be so kind to take it slow next time, and to be more encouraging.
What helped me was Him giving me compliments, telling me how pleased He is, how much I please Him, how much He likes it, how good I look - and most importantly, making it clear that He will respect me in the morning. As long as it was clear that He gets that I am not really a slut, I had no problem playing/being His slut.
Stripping got easier as familiarity and trust grew. Masturbating in front of Him, it stil makes me cringe a little, but mostly because I find it so boring and because I never found it to be something special so I am always lost as to what to actually do - its much easier when He gives me orders what to do, I even find it a turn on to perform for Him then. Exposing yourself and your vulnerability, giving away your pride - it is the hardest part about submission. Thankfully Himself seems to have tired of that game on a regular basis.
Good luck,
Adriana