question: i have been running since January and managed to get up to 6 miles . But now i am unable to run a mile without my right lower calf feeling very tight an heavy . I am trying ti train to do a half marathon in June . I also swim twice a week and have joined a milatry fitness group twice a week too . But my right leg is oreventing me from getting any further with my running . i have no idea why it has suddenly started doing this .