I guess I got a bit overexcited about my sore shin. Went to sports med clinic and had an xray. Xray negative, which for stress fracture is not necessarily proof you don't have it. Two spots of calcification showed up under the skin directly over the shin bone in the sore places. He and the physician's assistant did lots of poking, tapping, and twisting. Nothing hurt when they did that except the two spots. Dr. said I can run if it doesn't hurt while running. And he said, "You know what you're doing." He meant regarding increase in mileage, etc. Reassuring. He said that if I did have stress fractures it would not be due to overtraining, but to bone loss due to hormone changes. Recommended more calcium and weight-bearing squats to build bone.
So the discomfort gets less every day, which is also encouraging. I didn't run last night. Hoping tomorrow I feel even better and can run the race.