You should ask your practitioner these questions and trust her response. While there are some fairly definitive contraindications in Chinese Medicine they are more often stronger for some people and less of an issue or even important to disregard in other people. Only someone who is fully familiar with your case/constitution, etc. overall can truly provide an answer. Additionally with herbs any contraindications would largely be dose dependent and further related to the person overall. In short, there are few generalized answers in Chinese Medicine.
All that said, most herbs properly prescribed and used are safe. Avoiding herbs/formulas with very strong functions, particularly on the nervous and/or hormonal system, is usually preferred as are those with high alkaloid content. Yan Hu Suo, or Corydalis Rhizome, does have an active alkaloid content and is recommended against use in pregnancy certainly and some recommend avoiding during nursing as well. Most of the contrainidications for nursing are vague and less about passing through harmful actions to the child and more about possibly drying up the milk of the mother or flavoring the milk so the child finds the taste unpleasant or experiences mild disruptions in the digestive system. The few that could have more definitive statements about them are aloe, ephedra, garlic, licorice, rhubarb, parsley and sage.
To limit reactions know that most herbs, similar to most foods and drugs, will peak in your system about 45-90 minutes post consumption and peak in breast milk about 15 minutes after that. Timing of herbal intake and regulating proper dosage can generally avoid any possible complications.
Again, most are safe when properly prescribed, but you can watch for what are generally mild reactions in the child to know if you should discontinue use - these would be irritability/insomnia, diarrhea/colic and/or any skin reactions. Most of these are issues that children have anyhow so distinguishing the herbs role in them is often difficult. Any noticeable change in the child, however, should lead to the herbs being discontinued unless there is an extremely strong reason to use them at that time (similar to any western medicine).