How much vitex agnus castus (chaste berry) should I take?

I have been taking 660 mg in the pill form twice a day and I was just wondering if I should be taking more or less to help regulate my period? I have been off birth control for quite a few months and still haven't had my period. I have been taking vitex for almost 6 weeks now and haven't noticed any changes. Should I stay with what I am taking or increase or decrease the amount? Thanks!