Vitex was terrible for me- it turned my regular, happy cycles into full blown PCOS. I stopped O'ing the month I started Vitex, gained 40 lbs in the few months I was on it, and kept gaining weight for the first 7 months after I stopped taking it- until the doctors figured out what was going on with me. By then, I had gained almost 100 lbs, was insulin resistant, and my hormones were a total disaster.
I didn't ovulate on my own for over a year after taking that stuff. Ended up having to do IVF, and that's been a nightmare all of its own. Since then, I have come across other ladies who have taken it- both those who O'd before and those who didn't, who had similar weight gain issues, and who also developed insulin and hormone problems after Vitex.
Anyway, I know most women respond fine to Vitex/Chasteberry, but I always like to post what happened to me just in case someone else notices it beginning to happen to them. If anyone does, they should stop taking it immediately. It was a really scary situation and, 3 years later, I am still 60-70 lbs heavier than I was pre-Vitex and now I only O once every 50 days. I don't know if things will ever go back to normal for me.