Talk to Psychiatry on Brain Blockage

when my mind goes blank,l don't understand anything,even my periods.l'm unable to take care of myself .l have taking depression medication past five years.despite changing doctors twice .l haven't experienced relief form my mental blankness.when l met the second psychiatrist,that doctor also took my blood tests and urine test.all the reports were normal.but my blankness is persists.my mind gets so blocked that l struggle to utter even a single word.l feel completely blank.l am in second part of intermediate.In this condition,l won't be able to give my exams because of my mind is blocked.what should l do?l went to the doctor again,but even after visiting three times l ,m not getting any relief.