Breast feeding

Hey mommas. So my baby was born September 7th he’s almost three weeks now and since he was born I was pumping about 270 ml every three hours after about 20 minutes of feeding baby every three hours. My boobs were getting sore so I started only pumping once a day and now it’s seems like baby is sucking for about 40 minutes every half hour to and hour and I’m only able to pump about 70 ml twice a day. Any suggestions on what I could do to get more milk? I’m going to start pumping every 3 hours again and I’ll be cutting all juices and caffeinated drinks out of my diet, what else can I/ should I try?