Breastfeeding and pumping

Is anyone else breastfeeding and pumping when they can? I go back to work in a few weeks so I’m trying to build a freezer stash. I’m breastfeeding on demand and trying to pump for 10-15 minutes in the morning and in the evening. I only get about 1 oz per boob. Tips to increase this? Or is this normal while I’m still feeding her on demand?