I'm feeling really discouraged about my supply right now. My daughter seems to have a very random…

I'm feeling really discouraged about my supply right now. My daughter seems to have a very random eating pattern and I can't always tell when she's full because she tends to fall asleep. I pump after I feed her, but I can only maybe get an oz from each breast. Sometimes less.. Baby girl was 9lb 2oz at birth and was only 8lbs 8.5oz at 6 days old. My doctor acted worried and told me I may have to supplement with formula if she isn't back up to birth weight at our next appt (today, 9 days old). I'm so worried and nervous. She's been having about 6 poopy diapers and 6 or more wet. I thought that was a sign she was getting plenty, but now I don't have a clue. Does it sound like I'm not sustaining her? I'm so heartbroken over how this feels.