Pipimom,
Don't be frustrated. I had that experience before when my son was 1 and 1/2 month (tried very hard to pump for half hours and only got 1-2 ozs), but I insisted and kept feeding him directly. I stopped using the pump (partly because I was afraid to have so little milk each time) and feed my son directly for all the time until I was about to start my work. When my son was 2 months old and I need to work again, I started using the pump again and got 4-5 ozs each time.
So, insist!