dream or nightmare?

I had this dream. Some would probably call it a nightmare, but to me it was a dream. 

I dreamed  that I was with two girl and this boy. I can't really remember what the looked like... only that one of the girls had long pretty hair. She was skinny... she was me, just skinny and pretty with the long pretty hair I'm dreaming of having. 

We all went to this house. It was empty. Really empty except from the mattress that was laying in the corner. The guy, lets call him Kasper, stood in front of the mattress. The two girls were looking at him, then me. The one who looked like me, lets call her Linn, started to smile. Not as if she was happy and she was about to laugh, but she smiled in this creepy way. It made me frown. Then the other girl also smiled in the same way that made me feel unsafe. I looked at Kasper, his face was pail white. His lips had lost its color. Everything was grey. 

The girl handed Linn some knifes. They were sharp and pointy. They were in different sizes, most of them were small and looked to me the sharpest of them all. 

Before we even thought about what she was going to use the knifes for, she threw one directly at Kasper. It went through the air and cut his back open. She didn't really go for his heart. She wanted him to suffer, it was like torture. As she threw five knifes or more(time went really fast) I walked over to Kasper. Stood in front of him. I didn't think she would through any more knifes if I was there. I was wrong. The knifes came cutting my back open as well. Then... Linn threw this butcher knife, just before it would have hit me in my stomach, Kasper grabbed me, though us both onto the mattress, he shoved me closest to the wall and himself closest to Linn. More and more knifes hit our backs. There was blood all over the mattress. 

So my thought is; why didn't we say anything. This whole dream there wasn't one person talking. Other thought is, wasn't this a nightmare? The rest of the night I felt this huge pain in my back. I didn't dare sleeping on my back, I really believed that someone had cut my back open. I kind of wanted the whole thing to be true. I want a reason to my daily life pain. I want a true reason to my depression, self-harm, anxiety and my eating disorder. Nothing really bad has ever happened to me, except form the stuff my dad did and the bullying, but other than that nothing. Sometimes I wish I wasn't me. Not sometimes, more like everyday. I wish I had this pretty long hair. I wish I was that skinny. I wish for so many things to change on my body, and I feels so selfish to have all these wishes.