My sister did this. It was the case of the too placid baby. My mother started to basically force nurse her every 2 hours during the day. She started gaining weight. I would suggest dream feeding her in the night as well. If she is only nursing 4-5 times in 24 hours that will not be enough.
1-2 ounces when pumping is normal and not a reflection of low supply. Does she have a lip or tongue tie because that could make milk transfer more difficult. I would not move to formula but push nursing more.
Proud Mama to Hannah
(7/03) and Lily
Happy to be again after a bit of a break