I have only recently stopped taking Vitex, I took it for about 9 months to try and get my cycles under control, my first cycle on it was my longest ever (wow a whole 27 days!) but then they went back to there normal irregular short selves with no major change.
Vitex is supposed to work on the petuitary (scuse spelling) gland and make it regulate your hormones better. It's also great for older women for the same reason, my mum took it for a while after having a hysterectomy and it helped a great deal with hot flushes ect.
As you can see it didn't help me concieve...
Good Luck!