Night Terrors or Something More?

I don't drink or do drugs- I never have. I am fairly sane and normal. I am majoring in neuroscience, so you know I'm not unintelligent or anything. I am known in my family for waking up in the night, screaming my lungs out- I get an overwhelming feeling or terror and panic, and looming depressing fear that blankets me. For some reason this feeling will grip me while I'm sleeping and I scream- usually while jumping out of bed and running around the house. Sometimes it comes with an image that may or may not be terrifying. I suppose this is night terror disorder, though its rare for adults to have such a thing. However, I have also seen beings that I will never, ever forget. Two in particular stand out to me.

I once saw the grim reaper standing over my bed. He was cloaked in shadowy blackness and was even holding a scythe. He came with that overwhelming feeling of doom. My eyes were open, I was awake but not completely "conscious", still hovering in dreamworld. I was terrified to walk in the woods for days afterward. It had felt so real, that hallucination or whatever it was. I was actually wondering if it meant I was going to die. I tried to shake myself of those thoughts and think rationally.

A few months later, I experienced another being in my room. This one was humanoid and naked. It was a dirty dark tan color, with rough skin. I guess now that I think about it, it was comparable to the brown wandering creatures in the Silent Hill video games, only with moveable arms and much more thin. It was tall, and skinny. And it was climbing on my bed up to my face. It didn't have much of a face, or at least I didn't notice one. I was terrified of course, but not as terrified and I would expect myself to be. I was awake, and watching this thing crawl on it's hands and knees.