sleep disorder w/intense anxiety - what is it?

I have been struggling with this sleep disorder for about a year now. I haven't found a name for it online, so I thought I would detail the symptoms on this forum. If you have any ideas please let me know. It would be much appreciated.

It doesn't happen every night, but I think I have noticed a connection between it happening when I need to get more sleep or go to bed earlier. Regardless, it continues whether I am stressed or not... I can be perfectly fine, trying to get to sleep and then it happens again. Here's what occurs..

* Maybe 10 or 20 minutes or so into trying to get to sleep, I feel a 'shift' in my brain. I start to feel unreality and depersonalization - which is normal, if you're starting to dream. But I'm not, I'm still fully cognitive and awake.
* Sometimes I see flashes of white light around my peripheral view.
* I get intense chemical anxiety. I say chemical because I don't know how to describe it in another way. It feels like a shower of anxiety coming from my brain down into my chest. My head actually feels like it's tingling. It lasts for about 3 or 4 seconds, but occurs more than once.
* Speaking of, I feel a lot of heart/chest pain during this, and sometimes I think I am going to get a heart attack.
* Just last night I started to feel the anxiety in my brain stem area! Whoa..what is going on here?
* Sometimes if I open my eyes during this I see hallucinations. I've seen anything from black blobs on my walls, to a kitten grooming itself. It disappears very quickly. Again - I am not sleeping..usually all the pain and fear has kept me awake. I was having some other weird hallucinations last night too, where I felt like I was turning my head to the side but I wasn't.

I always feel like I'm going to die or that I'll need to go to the hospital because the physical pain is so intense during this, it's not prolonged but happens in waves or "flashes" as I call them. It has been keeping me up a lot lately, it doesn't happen every night but sometimes I can predict when I'm going to have an episode and it's really scary.

Any clues?? I feel helpless. I almost think I should see a sleep specialist to see what is going on with my brain activity at night.