Just wanted to jump in and say I agree with what's being said already.

I consider myself a pro-expresser (Brendan I expressed for 5.5 months and Tristan for a few weeks) Even when I was trying to express for Tristan so I could have a night out I was only getting 5-10ml and that's with all my little learnt tricks too! My point is that your breasts are making enough for what your DD is taking, so it will take at least a few days before you see results even if you were to express with every feed. So don't be too hard on yourself! And as someone said previously, you will never get out all the milk like D can