Why do I keep dreaming this?

While dreams are about impossible to decode unless you know the person very well, you can apply some things used in the Rorschach protective test. Which can get weird... but, the knives most likely represent two things, sexual desire and conflict. Them bleeding to death, this is a stretch, may have something to do with you feeling distanced from them. i don't know every aspect of your life so try to apply that to you situation. The house burning down is probably something to do with your values being challenged by this sexual desire/ conflict. The waking up in the hospital might have a lot to do with you not feeling in control of your own life or your situation. Being dehumanized may have something to do feeling like your changing into something else, and its not by your own choice, that goes back to both the bleeding to death and you not feeling in control. Its only information, again i don't know you but try your best to apply it to your situation. Dreams can be tricky. Look up Freud's theory on the Ego, Superego, and Id for more about what the conflict might be. Identifying your emotions is very important.