So the headaches and changes in reading habits, etc. started in "the past few months" and the eye exam was just outside that range, yes?

I think another thorough eye exam seems like a VERY good idea. It sure sounds like eye strain from a sudden shift in vision. Sometimes a person's vision can become unstable like that without any apparent reason and without any history of problems, either. It happens to quite a number of adolescents and college-through-graduate students.
HTH!

Schrödinger's cat walks into a bar. And doesn't.