Hi, and thanks for your medical question on eHealth forum!
Yes, there is a lot of promotion about this on net. However this has not yet been approved by FDA. However these so called natural products do not go through strict clinical trials weighing their benefits against their side effects and do not need clearance from bodies like FDA and other such drug controlling agencies.
Hence the safety of taking Vitex has yet to be confirmed. Long term side effects have not yet been studied. Hence it is advised not to take medicines or pills not approved by concerned authorities of your country. If at all you need to take these, it should be under strict medical supervision. If you have been trying for 14 months, then it is advisable you consult an infertility specialist or at least your gynecologist to find out why you are unable to conceive. Hope this helps. Take care!