I have been pumping a few weeks prior to my return to work back in August. I am using a PISA and lately, it seems like sometimes I can get 6 oz collectively in 10 minutes or so and other times it trickles out for 20 minutes and I have to get back to work. I also turn it up as high as the speed will go (gradually so it won't hurt) but even at the highest speed, it still feels slow. Is it me or the pump or me just getting used to the pump? I replaced the membranes last month and have not called Medela/gotten a replacement pump because I don't know "who's at fault" (I use it 4x a day on weekdays and 1x on weekends) ...thoughts?