There are times when my entire vision turns brown and i couldn't see anything for a few seconds. what might be causing this? do i have an eye disease?

Not sure: With both eyes having visual disturbance as you've described, i recommend that you see an eye md for an exam. These symptoms could be related to your migraine condition, however migrainous events do not affect the total vision in both eyes, usually only part of the vision of each eye during classic migraine. Call your primary doctor too to see if some medication you are taking is responsible too.