Oh dear!
I've had migraines since i was seven, and it was only two years ago i stopped taking the meds for them. However i don't know where mine come from either- it has been suggested 'STRESS' (although i don't know how i became stressed at the age of 7) and also as Abdominal Migraine- as i usually get stomach cramps, and other aches and pains with them. I know it's frustrating not to know what it really is, but i've not had one for a quite a long time now. I get the occasional with blackouts, but nothing as constant and blinding as when i was younger.

Maybe it is allergy related? And it's probably something you should take seriously? Have they mentioned anything else- medication etc?