You should increase your pump suction, after you achieve a milk flow "let down", and when it also feels comfortable and not painful.
When using a breast pump, start with a lower suction setting at first, then increase it as your milk starts to flow and you become accustomed to the breast pump.
Pumping your breast for breast milk should never be painful or cause any discomfort.
At first start off with a lower suction and faster speed which mimics a baby's initial feeding.
Then once you feel the milk flow, it is the "let down", you can then increase the suction level to a setting which feels comfortable and allows you to continue pumping.
Pumping your breast should never hurt, and you should use the highest setting that is comfortable for you but no higher if it hurts.
You can find your maximum comfort vacuum when pumping your breast by increasing the vacuum until the pumping feels slightly uncomfortable and not painful and then decrease it slightly.
Once your breast milk lets down, you can then increase the suction to strong yet still comfortable.
Then leave the speed on the highest setting during the pumping.
And if you use a non Evenflo brand of breast pump you can duplicate this by hitting the letdown/massage/stimulation button repeatedly throughout the pumping to keep the speed fast.