Running

I think I'm not doing it right, I run most of 2km these days and I'm not in half as much pain I anticipated I would be in.  So either I'm not running fast enough, I need to run a longer distance, run all of it instead of brisk walking some, run more frequently than just twice a week or I'm not meant to be feeling any pain. I will try and run 3 times a week without fail next week and tonight/tomorrow morning when I run, I will try and run at least 1km without stopping (mind over body or is it pain J). Currently it's taking me about 15 minutes to do the 2km distance.