Vitex ..

So I bought vitex about three weeks ago been taking it every day since I take two tablets in the morning on an empty stomach only problem iam having is wondering if I stop taking it the day I get in my fertile week or if I stop taking it the day before ovulation my period varies between 28 and 26 days started my period a today which is a day earlier I also take prenatal and multi vitamins via man E and evening prime rose oil and o mage 3 please so, one help me figure this out iam so lost