None of us went to the doctor, but at the time we all thought the illness was strange and not like any flu we had prior
Same here. That Saturday (it was like 1½ months ago or so IIRC) I just kept thinking that I am not feeling quite right but I couldn't really tell what was wrong, and I started even suspecting I've had a slight heart attack or something, due to the "odd feeling" in the chest and pain on my left shoulder (I keep hearing those stories that in a heart attack your left arm may feel numb etc., so naturally I always become alarmed if there is any pain on the left side of my body).
But then, I wasn't coughing or didn't feel trouble breathing, so not sure. But if the doctor said I seem to have pneumonia and even gave antibiotics for it, I guess that was the case then.
And, I have no idea how long it lasted. I thought I was already fully fine the next Wednesday or so, but then a week later I got e.g. a sore throat and a runny nose for one more week or two. Hard to say if they were about the same illness or separate cases, and whether they were related to corona at all.
In a way I would be a bit surprised if it was because back then there was only like one diagnosed corona case in Finland IIRC (the Chinese tourist some 900 km away from me), and I am not that social ie. not going to restaurants or big gatherings, quite much staying at home and even my workplace is in a remote place away from other people. So if I really contracted the virus from somewhere, it must have been in a supermarket where I buy groceries. But then, I would have expected lots of other people here would have had it at that point as well.
It is possible as you say, the virus was making rounds already before it became big news. Who knows, maybe it is currently at its second or third mutation round already?