Well i think it might mean two things: 1. You subconsciously or consciously feel suffocated by some aspect of your life. or, 2: You're secretly a little kinky.
what you might be experiencing besides the obvious interpetation of feeling held down in other areas of your life ,might be this is simple a case of astral calaspy ,some beleive we astral travel at night, that are subconscious/soul actually goes out of the body when we are in deep sleep or certain phases of conciousness .
most of us do not sense this coming and going as it is quite natural ,BUT some people actually get that feeling of being unable to move,breathe,or held down by the wieght of the body .like you describe it feels like someone on top ofyou and it actually is YOU ,trying to go back into the physical body .this is a therory of course but i have heard it described many times throughout my answering dreams ,so possibly this might alleviate your feelings of anxiety a bit ,just relax and realise it is nothing otherworldly it is just you [soul]trying to come back to conciousness .
hope this might help a bit ,at least it is another avenue to think about .
best to you
OK TOOTSE, HERES THE DEAL. APPARENTLY YPU SUBCONCIOUSE AND CONCIOUSE ACCADENTELY CROSSED WAVELINKS AND NOW YOUR FANTASISING ABOUT RUFF DOMINANT SEX WIH THE INVISIBLE MAN.......HA HA!!