I have a Purely Yours electric pump that I plan to use when I go back to work. I bought the Avent Isis pump to keep at home for quick pumping, and if I wanted to pump just one breast. But I can't get it to work. I guess I used to my electric pump. Milk flows out of me early and often with an electric pump. But I don't feel any suction at all with the avent pump and no milk comes out. I've taken it apart and put it back together a couple of times but no success. Is the Avent pump hard to use. What am I doing wrong?? Thanks for any input!