Need help understanding a really strange dream.

The dream occured after I fell into a light sleep. I was only asleep for about 15 minutes but the dream lasted the whole time.

It begins with me in my bed at night. I look up and a figure walks into my room. A shadow covers its face so I cant make out any features. It approaces me threateningly and I know it has violent intentions. I pull out a sword and chop its head off. After its head hits the ground I can clearly see the face. It was my face. I realized that was somehow a copy of myself and I killed it. I cough up blood and die. That's when I wake up. Very short and simple story, but I wonder what it means.