Vitex makes me bleed?

I just got off depo last month and I took vitex to help me ovulate. It was working great and I got EWCM a week of using it. I started my period the 24th and it kept going for over 1 week until one day I forget take the vitex and the bleeding stopped completely then I took the vitex in the morning and it started again? I stopped taking it but does anyone know why the vitex did that? I was taking like 1300 mg every day