I've been running for about 12 weeks and today for the first time I had to stop half way through my run due to a very painful "tight" calf muscle. I'm not sure what I've done but I can hardly walk let alone run. What have I done and what can I do to get it to recover quickly? Total rest? Stretching? A support sock/band? I really want to keep running and not miss too many days running. Help?!