Pain 😢

I have pain on the right side of my breast and a bit underneath, I've been nursing all day to try to drain as much as I can and have expressed milk too, and have done so to where there is no more coming out, but it's still very painful. I've done hot water and will do more hot compresses but what else can I do? Why is there still pain if I've expressed and kept expressing and nursing through out the day? Before when it hurt I drained all the milk and it was better, now it's not 😖