Exclusively pumping how do you build your freezer supply up

Help I just started pumping exclusively a week ago when my son started to get sick he's 1 month and drinks about 3-4oz. I tried pumping every 2 hours but I would only get a Oz from each side with a total of only 2oz every 2 hours and he eats about every 2-3 hours. So I found when I pump every 3-4 hours I get about 4-6 ozs total. What do I need to do to start building my freezer supply I plan on going back to work in a week and I only work about 7 hours which is 2 feedings but I don't want to give him formula any ideas on what I can do to build up my freezer supply. I've also started drinking mothers milk tea, eating oatmeal, taking the furngeek pills and anything else to help boost my supply