Oh gosh i know how that feels cus i always experience it. It sucks! Could be clogged ducts thus milk expressed is reduced. I would use hot compress abt 10-20mins prior to pumping. While pumping, i would massage the lumps gently in a circular manner towards the nipple. After pumping, i then use a cold comlress to soothe the boobs. Personally for my case, sometimes it helps, sometimes it doesnt. But i still do it anyway and pump regularly and sometimes cry cus its too painful :/. Hope u get over it soon!
Apply hot compression on it and hand express it out. And let baby latch . And continue hand expressing out. It happens to me once I skip 1 pump session. Really painful