Doctors are pattern matchers, your newborn symptoms could have been in their experience the baby not getting enough milk. If it wasn't the pediatrician, well, they are your best source for the baby's health, everyone else isn't qualified (including nurses, midwives, etc...).

Also, it takes a while for the milk to come in after the baby is born, it is an incredibly tricky process of getting the baby fed where nature doesn't do us many favors. The baby probably was hungry, the milk probably came in later than they wanted, but all is still ok. Finally, you know what goes into baby with formula, with breast milk it is much harder to tell, making the job of determining if the baby is getting enough much more difficult.

Breast feeding has benefits sure, but they aren't so much that it is worth starving the baby. It is a serious tightrope to walk, especially in the first few weeks before production comes in completely (if it does at all, many women have problems).