Still Not Over Having Sex Last Wekend

I am 22, I had sex for the first time a week ago. The man I met at work a year ago, he is married with kids. He came to see me unannounced. My roommate was out. He told me he wanted me to get nude for him, to undress and stand before him so he could look at me. He went on to tell me he had decided that I was the girl he wanted as a girlfriend.

The evening was slow, waiting for me to get undressed. I did, in front of him, one slow stitch at a time, he pointed to each piece of clothing. Once I was totally nude and he had looked me over he suggested we go to the bedroom. The sex itself was purposeful, not romantic. He asked or maybe demanded I tell him I was his girlfriend.

This weekend he let me know he was tied up with some obligations with his wife and her parents. I will not be his girlfriend, now I need the courage to tell him.