ESET Nod32 is one of the lightest antivirus software today. It has great detection rates and a really easy to use interface.. It should detect-block and erase when encounters with a virus.. Other than ESET, I would recommend 360 Total Security, Avira or Webroot SecureAnywhere as they are all easy, light and have good detection rates. You can try them yourself and decide which one is more lighter on your specific system.
If you feel that there are some infections on your system at the moment, why don't you check it with another "second-opinion" product like Hitman.Pro, Zemana AntiMalware or Emsisoft Emergency Kit and give us some feedback here?
I hope I could help, have a nice day
p.s : You've said that you have pop-up blocker, do you have and use a specific Adblock extension? as the most of infections today are coming via Ads and Ad-related websites. I can recommend Adguard, uBlock Origin for the extensions. They are both available at Google Web Store and Mozilla Add-ons page.