Sudden Change in Oxygen and shortness of breath

I've been diagnosed with COPD and emphysema for about 4 years. I've had several flares a year, mostly oxygen levels and infection causing hospitalization. Had a check-up a few months ago and all seemed well. Had another appointment a couple of weeks ago because I had started using 1 (I'm not sure of the word. Ltr. Unit, etc.) when doing housework, walking, etc. I took the breathing function test and it showed a decrease from 4 to 3. I'm home taking my third course of steroids and second does of antibiotics in two weeks. My breathing has gotten worse (approx. 3 units now) and I'm using the oxygen almost all day and definitely all night. Has anyone else had such a sudden drop that could shed some light on what might be causing it? I'm a reformed smoker and have always been active, but have slowly lost the ability to do high energy tasks and now almost none. I go back to the doctor on February 16 and am terrified of what he's going to tell me. Truth be known, I'm just terrified. I'm a first time poster.