I don't think you are suppose to use it. My doc always prescribes the Mini Pill for me while breastfeeding. It is a progesterone only pill. I didn't have to use a back-up method with it but sometimes it's recommended. BUT as soon as you stop nursing, you should get on a different pill.
Maybe call your doctor and tell him that even their site says not to use it during breastfeeding, and ask if there is another option!! I haven't used it so I don't know. I do know there is a low hormone pill you can take while breastfeeding, but you still need to use protection while on it. Sorry i'm not much help, but thats what I would do is tell your doctor and ask!