Is it normal to be raped in a dream by a woman/women?

For quite a while, I've been having dreams (more like nightmares) of being sexually abused/raped, taunted, manipulated, and blackmailed by women (I'm a man). Just recently, I read an article that the way I sleep could be the cause of it. Is this really possible? I've been sleeping on my stomach for quite a while, but I do flip over every now and then as well as starting on my back when I lay down at first. I wouldn't think this would be possible. I try to dream of better things, but it always comes back to this. A celebrity (athlete, actress, anchor/reporter, etc) or someone I'm acquainted with (coworker or classmate, etc) would be in the dream. I hate that I have these nightmares, and I want them to stop!