What Causes Headache And Flashing Of Vision?

Hi, I am a 21 year old male. 3 weeks and 2 days ago while taking finals exams and the day after my grandmother passed away I got a weird sensation in my head while I was taking a final where it felt as though I was going to pass out, I was dizzy and my vision was flashing. I went to a doctor and was told I was having a migraine aura. Other symptoms I have had were heart palpitations, fatigue and trembling. The symptoms continued and I went to physician, eye doctor and a neurologist who all said I am having a visual migraine or a migraine variant. I had an MRI which came back normal and am having an EEG tomorrow. The symptoms are minimized with prescribed xanax but have not gone away for now over 3 weeks. The worst symptom is the vision flashing because it constant, persistent, and noticeable. I also have costochrondritis, is there any way that can be connected to this? Mainly my question is, is it possible for a visual migraine to last this long or is this even a visual migraine? If it is what can I do to make it go away? Thanks for any help.