Blocked duct

Ashley
I exclusively pump due to my daughter having trouble with latching. Been pumping for 16 weeks. This week I have gotten a blocked duct 3 times. Each time it's in a different area of my breasts. I've used massage, warm compresses and pumped a little longer just to be sure I'm completely emptying. 
My question is do any of you have any advice to help prevent a blocked duct or other ways to relieve them?
Thanks in advance