My son is 7 weeks old and we have been lucky to have had a great breastfeeding experience so far. However, I have continually tried pumping with my Medela Pump in Style Advance pump and it has been very frustrating. When I pump I can barely get anything out. I have tried different shield sizes and nothing seems to work. I do notice that even with the small size shield a lot of my breast tissue is sucked in. I am at a loss on what to do, because I need to build up breast milk reserves for when I go back to work. Any suggestions are greatly appreciated!