If you are going to exclusively pump you REALLY need a hospital grade pump in order to build your supply and maintain it. You can also try taking fenugreek, alfalfa, blessed
thistle and mothers
milk tea and brewers yeast
I am doing the same thing and here is what I have done. I took fenugreek and alfalfa for a few weeks. Everytime Lily eats, I pump after. I don't really time myself but I pump for ATLEAST 20 minutes or until I don't get anything for 2 minutes or more.