I have a possible solution for you. What most likely is happening with your leg is that your tibia and fibula are possibly separating a little bit, causing pain and inflamation, and this sensation you are dealing with. Try using a simple wrap around the upper portion of your calf, to keep the bones connected properly. What you want to do is use something like a velcro wrap, about an inch to inch and a half wide. This strap should be snug under the knee, but not overly tight. With this simple wrap in place, I think you'll find the overall sensation of pain will go away almost completely, and you'll probably have a much more pleasant time driving.
I hope this helps.