I am exclusively breastfeeding my 5 week old and have just this week started pumping to try and get a supply ready for when I return to work in 6 weeks. I am only getting about half an ounce from each breast each time I pump, and afterwards my breasts are incredibly sore - not the nipple or areola area, but the breast tissue itself. Is this normal when starting to use an electric pump? I am using the Medela Pump-In-Style Advanced and I pump one breast at a time after nursing my son (usually about an hour after.)