I rarely get sick - I attribute that to having lots of colds as a kid (with 6 siblings sharing germs). Anyhow, I get a cold maybe every other year. Usually big things like an appendix flare up that woke me at 0400. Diagnosed over the phone but went away by the time I got to the doc. Got an awful headache, turned out to be viral meningitis (MRI, spinal tap). Wife and I got Whooping Cough 12+ years ago. Docs said no one gets that anymore. Right after that, there was an outbreak around us. Wouldn't wish that on anyone!
One time I had a cough after I had a mild head cold for a few days. Called the doc - said it was just post nasal drip, take some OTC meds. Cough got worse. Finally went to the doc, listened, took an xray and they said it was "walking pneumonia". I think they gave me something for it. Was about 10 years ago so I forget. They did say if a cough comes after you "got better" from a cold, probably pneumonia.