I get the pain if I overpump actually, like when I try to squeeze out every drop of milk when pumping. It’s like my body is telling me that I’m working the production line too hard. But when I latch more rather than pump, I don’t get such pain.
For the nipple pain, I just apply the lanolin ointment (I used Medela Purelan ointment) before and after latching. It helps a lot.