Female, 25, first aura migraine. shimmering that left field of vision after 20 min. is it hormonal? due for period in a few days. cause for concern?

Possible: Migraine headache is a one-side, pounding, severe headache with associated nausea, vomiting, vision change, and incapacity. Many triggers are possible: illness, menses, stress, etc. You're kind of lucky, because not everybody has the warning of an aura before their migraine. Consider taking a "triptan" if standard over-the-counter analgesics don't adequately manage your headaches.