Hey Emily, I've also been taking Vitex for the last 2 and a half weeks and I've had cramping every day as well, even before I ovulated so I know it's not a pregnancy related thing (dammit!) and I keep getting a stabbing pain to the left of my belly button

and feeling nauseous too. I hope it doesn't continue too! The Vitex made my 3 week AF go away, and I also ovulated 1 week after starting it. If I'm not preg this month, I hope I ovulate earlier than day 28 next cycle!!
Good luck with having a longer luteal phase!