Ankle sadness

This is very frustrating. I am totally addicted to running now. I feel great and I love the confidence I get by being disciplined about my workouts. But something has happened to my ankle. I can tell they have never been very strong. My ankles get tired very quickly and I have to just push through it. Being new to running, there were all kinds of thing that I don't know about... and stress fractures are one of them. It snowed Tuesday evening so I used the treadmill in the gym on Wednesday to run 40 minutes. My ankle started hurting a bit that evening, but I figured it was just sore. I ran again Thursday on the treadmill and by Thursday night I couldn't walk. I did not feel a moment of pain, such as a strain or sprain of the muscle. Also, they say that stress fractures happen more often when you go from indoor to outdoor terrain, as I did going from the bridge to the gym. So, I don't know what to do. I can't stand the idea of not being able to run for weeks. Just when I am getting started? I'm really upset.