OK y'all, I'm so confused about this. I am breast feeding my LO exclusively right now. She is 3 weeks old. I'd like to figure out how to pump to build up a little stash for emergencies and for DH to help out once in a while. I'm just at a loss of where to start. Should I even be thinking about pumping while she's only 3 weeks? She eats from both breasts at each feeding and seems like she empties them pretty well. When do I pump? After each feed? I pumped an hour after she feed and got like 1.5oz total from both breasts, but at her next feeding she seemed really cranky that she wasn't getting the milk. She didn't seem satisfied if that makes sense. Plus, pumping makes my nipples pretty sore for the next day. It hurts a lot more when she latches on. Does that mean I have the wrong size flange? Sorry if this seems all over the place, I'm just so confused!

Eta: I'm not going back to work, so I don't need to pump for that reason.