What can I do or take to motivate me to do work Im going to get fired if I keep slacking?

I sit at work and do hardly nothin all day exept be on yahoo ansers what can I do to motivate me to work is there a pill to help me concentrate on work. I seriously sit here all day from waiting for it to be 4:30 and leave. Everyday I say to myself Im going to do work but Im doing less and less everyday. Please Help Me!! :(