Increasing supply

I am 7 weeks postpartum and I get 3.5 oz per pump except my morning pump is about 4-5oz My baby is starting to take 4oz and i don’t know what else to do to increase my supply. I drink at least a gallon of water a day plus 1 big body armor ( and 1 soda most days) flange sizes are correct and i do a power pump every night and i just seem to get exactly 3.5 oz no matter what i do. Any tips to get my supply up? Anything is appreciated