Happened to me lots of time too. that background inaudible noise of people talking and the pressure on the chest - which doesn't hurt at all, more like compacted energies...

I'm been trying to OBE, and one of the stages is the sleep paralysis. According to OBE teachers, sleep paralysis is a body mechanism that prevents the body from moving while we are 'Sleeping'. So when you wake up in a sleep paralysis state, your body is asleep but your mind is awake, more like you are in between, that is why there is a chance that you can encounter or experience the astral side.

They also say that what you see or encounter in the astral depends on your vibration. If you are in low vibration, you will attract or see entities of same vibration - that is those gory or scary stuffs you see - the dark side. While if you are in high vibration, you will see light entities - such as the faeries or other fantasy creatures. Young children often sees them, because most of them still has that pure and innocent heart.

true experience of my sister when she was very young, she used to see outlines of small people (dwarves). and while staying in our province, she used to play along with 'invisible friends'.