Increasing milk supply on one side?

My lo is 2 months old and I am working again so I have to pump. I've been pumping for a little over a month. My right side has always been his favorite side and had always produced more milk. In one 15-20 min pump session I get 3.5-5 ounces out of my right side depending on if I fed on that side last. With my left side I only get 1-2.5 ounces even if I haven't fed on that side. I realize there's nothing to really worry about supply wise but I'm trying to make sure that I am able to build a decent supply for when I am at work. My work schedule is not always consistent or reliable so I never know how many bottles he will actually be needing while I'm working on any given day. Has anyone else had this issue and have suggestions? I drink tons of water and massage while I pump, it's only done