My reaccuring foot problem

I seem keep reinjuring my foot and I don't know how I'm doing it. I have been told by the school nurses that it is a pulled muscle in my foot, but you know how reliable they are. Since it's a reaccuring injury I think that it might be something more complicated than a pulled muscle. This injury always happens after I run and it just started last semester. When it starts it feels like I stepping on a rock, but if I keep running on it I eventually can't walk on it because it hurts so bad.