Vitex advice

I started taking Vitex this month to increase my LP which normally averages 8 days. I use CB advanced ovulation kits and normally get 4 days of high fertility before my peak which is normally on CD15 or 16.
This month I've had high fertility flashing smileys from CD7-CD16 (today) with no peak yet. 
Has anyone else experienced delayed ovulation with Vitex? I am taking 2 x 1000 tablets as per the recommendation on the bottle. Do I stop taking it in hopes of my peak showing up or do I persevere and wait the 2-3 months they say it takes to start having an effect?