Am I overreacting? (UPDATED)

My fiance found a paddle and decided he wanted to smack me on the ass with it. I asked him not to multiple times (at least 10 because he kept begging to do it), and he did it anyway. I got mad and accidentally yelled "stop" at him because of it. 
He's trying to justify his actions by saying, "it was a padded paddle and I hardly tapped you with it," and he's getting mad at me because I keep telling him, "Just because we're engaged, doesn't mean you're entitled to my body." He's trying to blame him getting mad at me on me because I "overreacted." 
I was raped when I was 15 (now 19), and he knows that. He knows how sensitive I am about the subject, and knows that it bothers me when he acts entitled to my body and when he does stuff (pertaining to my body) even though I've and him not to. 
Was I wrong for getting mad?
*** Update ***
We talked things over, and we both apologized. (Me for yelling because I feel as though you should never yell at your SO because my ex was abusive, him for doing that after I asked him not to) 
He also apologized because he isn't able to fully understand how something like that can upset me so much because he hasn't been through what I have, and that he'll start listening more and think more before he acts. 
This isn't something that's constant, it's a once in a while thing that happens because it slips his mind that I'm way more sensitive about things like that due to the situation. And honestly, sometimes I'm okay with situations like the one today and others I'm not, so I can see how he can be confused and maybe even a little frustrated with me. 
I'm so glad to have someone that I can work through problems with rather than someone who just gets mad and leaves.