Oh, PSA
I finally figured out what was causing the migraine (which went on to reach DAY FORTYFUCKINGONE). After seeing a neurologist, getting an MRI, developing fun additional worrying symptoms like joint pain, and generally freaking out, I finally solved the puzzle. 'twas the butle - I mean, vitamin D what done it. Recommended by not one, but TWO doctors, mind you, neither of whom mentioned this might happen at the outset, nor suggested it might be a factor when I mentioned having issues.
So, PSA: if you develop weird symptoms suddenly, leave no supplement or medication unsuspected, because your doctors, sadly, WILL.