And the doc says.....stress reaction.
He showed me on the MRI what he was looking for. Bones are supposed to show up all gray on an MRI. Partway down my tibia are big areas of bright white. That, he says, is inflammatory fluid. Oh yeah, that was also present on the side of my calf, which means shin splints. Of course.
At first I actually felt relieved and validated - I KNEW this experience has been too ridiculous to be chalked up to shin splints. And a stress reaction in that bone totally explains the pain, instability, and weirdness I've been feeling for weeks.
When I stopped, I realized that I had 5 blisters on my hands. I gave myself more blisters in one hour than I did while training for a marathon. Gaaah. Maybe I DO tend to overdo things. My high pain tolerance and stubbornness are gonna kill me one day.