Help! I think I may have a virus.

In the past few weeks, I've noticed some weird happenings and wonder if I have a virus or if this pro (2010) is ready to give up the ghost? Applications automatically launch, music plays randomly, when it hit command + T to open up a new window there is hesitation and the screen is blurred, when I leave the computer up for a long period of time while not using it, downloaded podcasts appear in multiple squares across the entire screen. I was informed that anti-virus software does more harm than good so I've never had any.