Hi, I'm Thinking I Have Walking Pneumonia, I Just Wanted

Hi, I'm thinking I have walking pneumonia, I just wanted to see if I was correct. Anything more than mild activity (walking up stairs of uphill) causes significant shortness of breath. My resting pulseox is in the 70s to low 80s, it is normally in the low 90s, or maybe high 80s. After moderate exercise I can feel out of breath and on the verge of passing out if I don't stop and rest a bit and breathe. Breathing normally is not painful, but taking deep breaths is painful - like a burning pain. Most noticible when taking a breath deep enough to cough. No post-nasal drip or any other nasal symptoms. I had a very bad cold/flu (seemed a combination of symptoms) back in early June that really wiped me out. I really hadn't regained full strength by the time this started about a week ago. Still feeling very tired/weak.