Shortness of breath 5 days, chest xray normal ddimer negative feels as though someone is sat on my chest oxygen sats 100 cannot sleep because of it?

Some possibilities: If I was seeing you as a patient with that story, I would be running an EKG, checking your blood counts (low blood counts can cause shortness of breath), and taking you for a walk while measuring your oxygen sats (as many heart and lung conditions can present as a significant lowering of this number with exercise). Anxiety can cause SOB and could keep you awake, but shouldn't wake you from sleep.