What Causes Pain In Calf?

I have had a pain in my calf for a few weeks that sometimes moves to a different spot. Sometimes the pain is behind my knee. The pain is more noticable when I am in bed. I also have had some buzzing/vibration sensations in the ball of my foot and toes on the same leg which happens every fews days that can last from minutes to hours each time. What could be going on?