Jules, it's certainly possible that, for whatever reason, you were unable to produce enough milk to feed your baby. You say you did everything right, and I believe you.
I also believe we are lucky to have formula for moms who can't produce enough milk.
But there is usually (not always) a clear reason WHY a mom can't produce enough milk, such as improper latch-on, not nursing enough, not getting enough rest, dehydration, having undiagnosed illness that inhibits milk production (such as celiac disease, hashimoto's thyroiditis, diabetes, and other autoimmune disorders), having been given medication that inhibits milk production (like magnesium sulfate), even stress can be a major factor for some women.
Another issue is separation of mom and baby. I produced way less milk when I put my baby to sleep in a crib. Sleeping with my baby and wearing the baby instead of pushing him in a stroller = instant 30% increase in milk production.
I'm not writing this to imply that you didn't do any of this. I'm writing it for the benefit of any reader who assumes it's common and normal for a healthy nursing mom to not produce enough milk for her baby.