Has anyone had success lengthening their Luteal Phase with Vitex?

I’m desperately trying to lengthen by 8-9 day luteal phase. My period comes like clockwork every 30 days but I ovulate on day 21/22. I’m assuming my progesterone is low so I have tried Vitamin B6 and C without any luck this month. I’ve heard good things about Vitex so just wanted to see if anyone else has had success with it? Did it help you get pregnant?