Vitex stop working for you?

I hear alot of success stories about Vitex. So i tried it and it worked i was so happy my period came for 2months in a row and on time after yearsss of me never getting my period but on the 3rd month of vitex my period did not come. I would like to think im pregnant but a couple of at home pregnancy test have been negative (it might still be too early) soooo does that mean vitex just stopped working for my body?

Has anyone have vitex just stop working for them?