Baby fell off the growth curve

Megan

My son was born at 34 weeks and was only 3lbs 15oz because he stopped growing at 31 weeks. He’s over a month old and was released from the hospital at 3 weeks old weighing 4lbs 12oz. When he was sent home I attempted to exclusively breast feed plus feed him the 2 bottles of preemie formula he needs. Well, over a week after he was released he was only 5lbs and they’re very concerned he’s not getting enough from me because of his lack of weight gain and over sleepiness. So I had to start pumping and feeding him a bottle after he breast feeds for 15 minutes on each side. I can barely pump 10-20ml after breastfeeding but he takes 30+ml after. My freezer storage is dwindling because I can’t find time to pump after every single time he feeds because my husband works 12+ hour shifts M-F and I have 0 family or friends in our area to help me out. I’m so scared I’m going to run out of freezer stores and not be able to feed him breastmilk all the time. I’m not sure what to do and any and all advice is welcome