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(CNN) -- Actress AnnaLynne McCord wants victims of sexual assault to know they have a voice.

That's why the "Dallas" star is opening up about her own assault in the July issue of Cosmopolitan magazine.

McCord revealed that at age 18, while living in Los Angeles, a male friend assaulted her in her apartment. As it was happening, she said, she wondered if she was somehow to blame.

"At first, I felt so disoriented and numb, I closed my eyes and pretended to be asleep," the actress said. "I wondered if I had done something to give him the wrong idea. I felt afraid of making him angry. Believe it or not, I didn't want to offend him."

It was during her role on "90210" a few years ago, she said, when she broke down during a scene involving the rape of her character.

"My castmates thought I had done a great job playing the part," McCord said. "They had no idea that I had actually been sexually assaulted by someone I knew in real life."

The actress also details what she said was a childhood of strict discipline and beatings from her parents and how she once considered suicide.

Now she feels it is time to speak out, she said, to aid other women.

"Most of all, I have my message for women and girls: You have a voice," she said. "Don't put yourself in a box. Don't let the polite lies of society silence you. Honestly, I would endure everything all over again; it has led me to my own revolution."

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