Recently bought a carinthia gore-tex bivvy, tried using it just indoors for the first time on a carpet. But for the life of me, I could not fall asleep. My back and shoulders were in a constant state of needing to be popped (its hard to explain) and more importantly, I couldn't really fucking breathe inside the bivvy. I was laying in it with my head as close to the small opening at the top as possible but it still just felt like I was breathing in my own expelled air over and over again. Only violently moving my legs around seemed to pump fresh cold air inside the bag which gave me some comfort for like a whole 2 seconds before going back to breathing in my own air. Opening the zip up further helped only a little bit, but it still wasn't good enough to actually fall asleep for me. Opening it up any further and I might aswell just sleep with just a blanket on me, kinda defeats the whole point of having a waterproof bivvy.

Am I using it wrong?