What am I doing wrong??

When I pump on my left, I get plenty of breast milk. When I pump on my right, I get maybe half an ounce and then nothing. I use my fingers to express after, and there is still breast milk squirting out. Why won't my pump finish expressing my right side.

My baby can only get a bit out of the right, too, before she gets upset. After this, I can still express milk by hand. I don't know why. My left side doesn't have this issue.

Any ideas about what's going on or what to do??