Agnus Castus/ Vitex Help? holland and barret only 4mg??

Sarahh

Hey guys, im ttc but missed my period last month, turns out i have a cyst on right ovary. No sign of period at all. So im trying to take Agnus castus from HOLLAND&BARRETS;, however the tablets are ONLY 4mg?! From doing some research other women take up to 1600 mg a day. have i wasted my money by buying 4mg tablets?? Anyone?