I certainly agree with dr.Andrews, however, i feel that you should perhaps notify your physician about the true location of the pain, and let him/her know if the pain gets better when you sit down, and worse again, the further you walk.
Radiating pain from the buttock area down to the back of your thigh and then occasionally all the way down to the calf can be the result of a lumbar spine problem. If the nerves from the lumbar spine are compressed (so called 'spinal stenosis'), walking is usually affected the most, and leaning forward over a shopping cart makes the pain typically better. Also sitting down makes the pain go away very quickly. Have yourself evaluated soon!