I have had um TWICE, once as a sophomore in track and then the next year as a junior. The one as a sophomore ended my running year cos I was on crutches through the entire season but as a junior a year later I was able to come back near the end of the year ans still won state meet in the mile.
Mine were caused (according to the doctor) because I was running too hard. I don't think so because I was running 25-35 miles every day through the winter and had no problem. It was just when I got on the track that it suddenly hit. The military gets um all the time when they get raw recruits out on 50 mile hikes with a 75 pound backpack. Anyway, I am not sure doctors are really that good with stress fractures. Everything is diagnosed as a stress fracture now days. They were rare back in the '60s.
Mine took about 7 weeks to heal the first time and about 5 weeks the second time. The second time I wanted to make it back in time for the big meets at the end of the season so I "pushed it" a bit. I ran on soft dirt piles after 3 weeks on crutches. The doc finally gave his OK to run again cos I told him there was no more pain. (I lied a bit). There was a small amount of pain still but it went away when I got into the races.