Loose/floating shifter

While I was driving to work today, my shifter just all of a sudden wouldn't go into any gear, and right now I think it's stuck in 3rd. The Shifter is just basically floating and not going into gear. I can go around in a circle with the shifter. I was wondering what would cause this. I haven't tried anything to fix it. I am just wanting to know how much this is going to cost me, or what I should do next.

Thank you