Do you have a neurology diagnsosed migraine? If so just reiterate and state that you suffer from migraines. I also had the headache DBQ doing my exam and the examiner stated in the DBQ in many places that I suffered from migraines separate from daily headaches, he stated how often I get them and the severity, in the end I was rated for migraines properly.
IF WORSE COMES WORST, you can do a VARR and add letters from your neurology and (hopefully you have been told to keep a migraine journal) your logs of migraine attacks to correct the rating.
They key point is to have your migraines diagnosed and documented by a neurologist - Neurologists treat Migraines and carry the most weight in these conditions. PCMs usually try to treat headaches, headache treatments can actually increase migraine occurrence and severity.