Vitex and OPK

Hi,
I generally have a cycle about 28-32 days long and ovulate on day 18.
I started taking Vitex this month to try and regulate etc.
But I ovulated on day 21? 
Has anyone else ovulated later on Vitex? 
I have also noticed LH surge for almost a week (only low) since maybe day 14? Until full positive on day 21?