Letdown issue in one breast...

[Green Decals]

My left breast lets down fine for DS and the pump, but not my right one. DS is super fussy at the right one and when I pump the flow is very slow, with really thin streams, and I can't pump ver much - less than 1/2 what I get from the left (which is usually only an ounce anyway). It seems to be getting progressively worse, probably because he's wanting to nurse less on that side. Any ideas on how to address this?