Supply question

Hello ladies, So have a 3 week old that has been EBF. I have been trying to start pumping after feeds a couple times a day so i can leave a bottle for my husband to feed her at night as well as maybe get a little extra to freeze. For example this morning she nursed on one side then i pumped both for about 20 minutes. Each side only pumped just under 2 ounces. Does this seem ok? I know she eats well. I can hear her gulping and swallowing and she is gaining weight. Is the pump just not effective? I feel like i was able to pump more last week than this week too. What do you guys think? My first 2 kids were formula fed so this is my first breastfeeding journey.