Regardless of the origin I want to give you a little information and I do hope it helps you in some way:
1) Hypnagogic hallucinations are common when you're in the trance state. Not everyone is aware of this until they start to do consciousness and awareness work. This is why many ancient disciplines discouraged this type of thing until you had reached a certain 'age' or 'stage' in your training. They are caused by your brain. The information used can be from your subconscious. But here metaphysics come in: Sometimes the information in your subconscious or unconscious mind can come from the astral, or 'akashic records'. So it is possible that you are overshadowed by some entity, who is taking advantage of what your subconscious had witnessed. (Which is why I no longer watch horror movies. Too much stuff for me to have to look at again, in the middle of the night, while paralyzed. No thank you.)
If you know that you have a weakness (i.e. you need your sleep) be aware that in your case it can be dangerous because it leaves you confused. This is good, because you know that your symptoms can be managed, and you are not at the mercy of something outside of you. In my humble opinion, fear is the worst thing.
Even if you are hassled by something astral, just knowing these things can help you. And countermeasures are definitely not going to hurt- there are things you can do to protect yourself from any possible entity that may be trying to take advantage of you.
Here are some: http://www.astraldynamics.com/tutorials/?BoardID=10

And, don't do drugs- In your situation they can only make things worse.