There are some supplements such as fenugreek and blessed thistle that are also supposed to help boost
supply. You can also try
pumping more frequently, such as every two hours or so.
When a baby breadtfeeds, they have cluster feeds constantly as often as every hour or less. This helps to signal to your body as well to produce more. I'm not sure about pumping much beyond this since I rarely use mine, but there are many others who have done it that im sure will respond. Good luck.