My baby girl was born prematurely, and had to spend time in NICU, so I had no chance to breastfeed her until we came home. When she came home, my milk supply went up (well, along with sorer nipples) with the increased frequency of feeding (vs pumping).
I was determined to go exclusive, but recently her appetite shot up, and I wasn't able to keep up with her (she keeps crying for more milk and she unlatches from breast), so I had no choice but to bottle feed formula to compensate, or I'm afraid she might dehydrate or go hungry
To increase my supply, while she bottle feeds, I pump. After she BF, I pump. When she BF one side, I pump the other side. Basically, just pump pump pump when she isn't feeding. This has increased my milk supply.
I usually pump 15 min only, because that's when most milk already pumped out.
30 min quite long, does it worsen sore nipples? What brand of pump are you using?