I think my mac has a virus

I know they are extremely rare for Macs but I believe one might be one here. I was working in programs then I checked my dock and it showed no programs were running even though I could move the windows around and work in those programs. So I restarted my mac and it was weird. My background had been changed back to the default background. I kept hearing skype noises and Skype wasn't running so I tried to launch it and it said another Skype was already running. I tried to launch Google Chrome and it would bounce once but not load. I just restarted my mac and the background is still the changed one but now I can launch Chrome. Any ideas?