I don't recommend herbs because there are no efficacy studies done on them and most are also messing with your body in one way or another in order to actually make you not conceive. Certainly they seem to be much better than synthetic hormones, but why mess with your body if you don't have to?
As a few people touched on, the sympto-thermal method of fertility awareness is a really great and effective way to manage fertility - well worth the time to learn. Basically, it's all about finding when you are actually fertile (or your partner is
) and during that tim either abstaining, using alternate sex, or using a barrier method. It's NOT the same thing as the rhythm method because it's based on what's happening in your current cycle with your hormones and not how your cycles have behaved in the past. That's why it's 99.6% effective (as long as you learn it well and use it correctly).
I teach the method and have used it myself for well over 4 years. You can learn more at my website: http://holistichormonalhealth.com
Feel free to let me know if you have any questions!