Erotica....bf?

Okay... Me and my bf have been together for about four years now and im a book writer. Nothing ever published or shared outside of some writing website. My boyfriend sneakily took a peek at what ive been writing. It was a sex scene, specifically it was one of our really mind blowing sex one night. He blew.

He was offended that I would write something like this, and I should keep our sex between the sheets and not on paper.

I got mad at him because I am a twenty three year old woman and he should not be telling me what I can not do especially if im expressing myself through writing.

Thoughts?