Mailbox is filled with emails from "unknown"

For several days I've been receiving hundreds of emails from "unknown sender."

I have done everything that gmail recommends - i've changed my password, marked all of the emails as spam, and deleted them forever. I have blocked them from my Outlook. I think that something must have infiltrated because I can't access all of my documents normally. My document set up looks different now - a little circle before each file and folder, and a different font than I've ever seen before. When I go to click on it to attach to something, nothing happens. Very frustrating! Any thoughts? I downloaded virus barrier express but no files have come up as defective.