I think anyone who has mentioned sleep paralysis is right on the money, having experienced this myself.

Avatar, do as another person said and search for "Sleep Paralysis", it's been discussed by me and others several times in this forum, you can read about our experiences and you will see that we have all had similar things happen to us as they have happened to you.  I must say I raised my eyebrows somewhat when you concluded to yourself that dmt entities had transported from another dimension and locked into your energy field and whatnot, but I guess I can sympathise because it is very scary and unnerving, and if you haven't ever heard of this before then you have no idea why it is happening to you - I myself thought I was becoming mentally ill and kept it entirely to myself for months because I didn't want people to think I was psychotic, and I didn't want it on my medical record.  Then I stumbled across a group on facebook about it, read all other peoples stories, and the relief that it was a common occurence for hundreds of thousands of people was comforting in the sense that I knew I was not alone.

A lot of people find there are triggers for it, mine are cannabis and sleep deprivation, my most recent incident was a few weeks ago going to sleep after a heavy night of alcohol the night previous.  Eventually you will stop being scared, and instead, you'll get mean with it, this is what happened to me a few weeks ago - I felt the paralysis, something shaking me, felt a 'presence' and I was just like "FFS, I'm tired, just piss off NOW!!!" and told myself to wake up, and I did, and went back to sleep without incident (normally going back to sleep just puts me straight back there), so I guess the message is, I know it aint easy, but fight the fear, and take control, find out your triggers if any and do what you can to avoid them, and good luck.

Methtical