breastfeeding milk pump help

So my baby girl is 4 months now and I exclusively feed her my breast milk. She eats from me and from a bottle when I have to go to work. I try to pump every 2 hours all day and night when she doesn't eat from me but i cant seem to build a good supply.... help? I take almost every supplement from Legendairy Milk but cant seem to pump more than 3-4oz from both breasts and sometimes even when i stict to pumping every 2 hours i only get 1-2oz. I've been told that it's normal range but my girl eats a lot and takes 5-6oz in a bottle a feeding and i struggle so much to have a little supply in the fridge for when i have to work. Does anyone have tips or other supplements i can try to help? I also use the momcozy m5 pump and know my flange size