Do you have a short LP? As long as you have a LP of around 12 days you should be o.k without taking it.

I had an LP of 5-7 days (breastfeeding) and after taking vitex it lengthened to 10 days and then a bfp. I was told to take it the whole month, but especially from ovulation to AF. I took it until about 6 weeks pregnant, cutting down the dose to every second day before I stopped.