For The Past 2 Months I Have Noticed Pain In

For the past 2 months I have noticed pain in my left calf and behind left knee after walking for a period of time, lets say walking around the office at work or even doing yard work. Today I spend about 4 hours doing yard work and holding the pain.
The pain was so bad I had to stop. took a shower and sat down. Suddenly a rush to my head and even felt the sides of my head numb.