Is my sex life my parents business?

I just turned 21 and I work two jobs and go to college full time. I currently live with my parents but I'm working on getting my own apartment. All my life I never really got sex Ed from school or my parents. The only thing I was told was don't do it. Growing up as a teen, I was kind of scared about having sex. It was between the whole having a baby and disappointing my parents. Even my first year of college I felt every guy who wanted to "hang out" was only looking to get me into bed. It scared me. The first time I had ever had sex was at the age of 20. I had lost my virginity to a friend that I had trusted. We weren't in love, but I felt that I was ready. Which I believe to be most important. Of course we were safe and used a condom. I didn't tell anyone I had lost my virginity because it's a private matter. My mom and I were talking one day and she asked me if I was still a virgin. I didn't want to lie to her so I said no. She went ballistic. She told me what a disgrace I was and that I was considered a slut. My friend I had lost my virginity to was about 4 months ago.   It hurt  hearing my mother call me a slut, but I thought, should she be really mad at me for having sex as an adult? Is it really her business? We used protection and all. She's tried punishing me for having sex, but isn't that ridiculous? What do you think?