Has anyone else had a problem where their pump suddenly stopped being as effective? I have been exclusively pumping for 4 months and I pump 4 times per day for 30 minutes. The past week or so the pump has not been emptying my breast the way it used to. I still feel full after pumping, even though the milk is not flowing by the time I stop. I have changed the duck bills, backflow valves, hoses and tried different flange sizes and changing the suction and speed. Before bed I had less than 3 oz out of one breast when it would normally be 5-6. I had a hard time sleeping because i felt full still. Any tips? I have a Lansinoh pump.