Help needed on pumping!

My son is about 3 and a half weeks old. I had planned to start bottle feeding breast milk (along with continued breastfeeding) at 4 weeks. That way my husband can do some night time feedings, and we can get baby used to taking a bottle for when I go back to work. However, I can only pump 5-15 ml at a time. I have an electric Ameda pump I got through insurance, and it was somewhat painful to pump, so I purchased a manual Avent pump. Both have the same pumping results. My son is able to get what he needs from breastfeeding, but for some reason I can't pump it out. The Ameda pump came with flanges size 30, 28.5, and 25 mm. I felt like the 25mm was too big and sucked more of my areola in, causing my nipples to be very swollen and very sensitive after pumping. So I then bought the smallest size they have available, a 22.5mm. It is somewhat more comfortable, but my nipples are still sensitive and a little swollen after. that's when I bought the manual Avent pump. The flanges on this one are 19.5mm. It's much more comfortable, but I'm still getting the same results. I'm feeling a little discouraged. Any advice is appreciated!!