Hey guys

I just had my baby girl on March 18th. She has lost some weight and the pediatrician wants me to supplement with formula if it keeps happening. I have been exclusively breastfeeding since I been home from the hospital. She told me to watch for her ques rooting and all that. Today I have been looking at her a little more. She just ate 15 min on one side and 30 min on the other. I just set her down and it still looks likes she is hungry. Is that possible? She also told me to pump so we can see how much she is getting. I pumped both sides for 20 min and only got a 1/2 oz out of each breast. Ever since she ate now she is spitting up.

What should I do guys? I really dont want her on formula.