Just wondering if I'm the only one around here not using any AV for a long time.
you aren't but if you are using Windows and no AV then you are a fool.
AFAIK, you can only get your virus on the internet (unless I'm underestimating USB's key viruses).
you absolutely are underestimating USB key viruses! stuxnet infected airgapped computers using a USB key.
Chrome pimped with Adblock and keeping myself far from the "dark side" of the web, I've never had any problem
while this helps it won't keep you completely safe.
Add to this the new lite Microsoft Security Essential (intagrated in Win8) to the lot and I'm surprised those company are still in business.
i'm not surprised at all. windows defender only detects ~75% of malware. at any given time, MS is about a year behind the AV curve.
there is a good chance you are infected with some malware.