Suggest Treatment For Pain In The Calf Muscle

I have pain on the side of my right calf muscle, when I sit or drive for long periods of time. It is located at the top of the calf just an inch from the bottom of where my knee bend on the side of my leg. If I apply pressure to the spot it relieves the pain for the moment but is very tender to the touch.
My leg needs to stay straight to not experience the pain.
I have tried applying a pressure strap and it relieves pain but does not eliminate it.