You don't state your age in this question. This would help to try to pinpoint what might be causing your problem. Blurred vision
, loss of vision that precede the onset of headaches
seem very much like migraines barring any other major neurological causes, such as stroke, seizure or brain tumor
. This said, you need to see a good headache neurologist
for a proper consultation on this matter. If this is a migraine it can certainly be triggered by the hormonal fluctuations of the premenstrual and menstrual times of the month.