New Mom Pumping question

Kelsey • Wife of Nate since June 29, 2012. After two miscarriages in 2012, our son, Alex was born January 24, 2016
My little man was born 1 week ago at 32 +3 weeks. He's doing really well but he's in the NICU, he never needed oxygen and he's down to just a feeding tube and no IV. I've been pumping since the day after he was born, I'm only able to pump 1-2 oz (combined from both sides) every 3 hours. This is my first baby so obviously first time pumping too. I'm just wondering if that is normal or if I should be getting more by now. I've been pumping for 15 min on each side, should I be pumping for a longer period of time every 3 hours? Thanks!