Sometimes when I pump, I get no let down at all. Even if I keep at it for twenty minutes or more, I don't get one single let down, and I get hardly any milk. Other times, though, I'll get three let downs in 20 minutes and pump 2 oz total (my LO is a month old). Any suggestions? I try breast compression and get a few sprays, but even those stop within 15 seconds.
Edited to add: I'm using a Medela Symphony, on rental.