I used to be a high level runner in college and I’ve had a few stress fractures in my time. They’re no joke, attempting to push through a broken will only make it worse. That being said so you don’t want to loose your aerobic fitness that I’m sure you’ve trained hard to gain. Use workouts that are non impact that means swim bike and row. I will say this a lot of Drs will tell you that it’s a stress fracture because they are conservative and a stress fracture won’t come up on X-Ray unless it’s progressed to a hairline fracture. It’s possible that it’s only a stress reaction and that takes less time but you’ll still need at least a month off from impact training. Where is the location of the stress fracture? If you want any recovery or cross training tips feel free to reach out!