Hi Sarah,
Growth is dependent a lot on many things. The mammary system is several levels of milk ducts shaped like an umbrella. Growth is a time based process that takes months. In order for there to be growth the mammary system first has to mature, the ducts need to prepare for growth.
A good pumping schedule involving stimulation and pre-expression and stimulation and post-expression along with pre and post massaging I’ve found to be the most rewarding.
Once the mammary system is matured you can add Domperidone, and a couple supply supplements, but the pumping routine, pre and post is essential.