Hi there Speaking from my experience back in 2009, before the birth of my first , it took me 9 months to establish a 'normal' cycle of about 35 days long, as they were ranging from 70-90 days! It was only after taking 1,500mg Vitex a day from AF - O day that sorted it all out for me, and I was pregnant the second month of having a 35 day cycle from using it - great stuff! Some pills have been known to affect women in this way, taking time to return to normality, and I was just 21 at the time so age wasn't even a factor. The Vitex didn't give me any side-effects personally, I think you have to start taking it to be able to decide whether or not it's right for you.
I honestly don't know quite how much Vitex is said to 'sway' but I can tell you that taking it resulted in my first - Best of luck! x