It should be the easiest, most natural thing in the world. Or so it seems.

But here I am, home from the hospital and my newborn daughter is struggling to eat. Her movements are frantic. She gnaws at my chest, my lip, even my nose, desperate for milk. Who knew that something so small could be so strong? We try again. When her forehead furrows and she pouts her lip and begins to wail, it is all I can do not to join her. I am her mother, she is helpless and hungry, and I don’t have enough milk to satisfy her.

For all the talk and preparation for the challenges of pregnancy and childbirth, the most fraught aspect comes after. The question of how we feed our newborns is rife with judgment and has been for generations, with expectations that get to the core of what society expects from mothers — and what I expected from myself.

Though I assumed that breastfeeding would come “naturally,” I suppose nothing about the process of becoming a mother was natural. For years, I had wondered whether I should have a child. Though my life was comfortable and full without one, with a partner and jobs on two coasts, I feared the regret I might feel if I never took the chance to know what it was to love someone so small and so sweet.

But as my due date approached, I would have gladly extended the gestational period so that I could gain more time before the baby came. I would have been happy to continue to grow for weeks, months even, if that meant I did not have to find out what happened next, if I could continue my life as it was.

Of course, none of this was under my control. One Saturday, at 38 weeks, I went in for a scheduled ultrasound and learned that I would not go home until the baby was delivered. That was that. I was powerless. And just a day later, there she was. Wet and screaming and perfect. Tiny and terrified and naked. And maybe not in that moment, but in the moments that blurred into hours and days later, it took my breath away to realize that there was so nearly a world without her.

That is maybe why I wanted so much to breastfeed. I imagined that I would watch her grow and to know that despite the uncertainty, despite my fears about the way that this new human would upset the life that I had built over the past four decades, my own body was able to feed her. She deserved that much.

A day after we returned from the hospital, a lactation nurse came to our apartment. She was a few hours late and I found myself counting down the minutes until her arrival. Just days earlier, I would have tried to fill the time with something productive, with writing or reading or emails, but now all I could do was wait, as though my very self was defined not by writing or patients or procedures but by ounces of milk.

When the nurse arrived, she lit candles and told me that while I breastfeed or pump, I should think about my baby and even look at photos or watch videos of her. The love will make the milk flow more freely, she told me. Though I am a doctor, I didn’t even think to look up any data to vet the statement.

That night, with my baby sleeping fitfully in the bassinet, I placed one hand on her swaddled belly while I watched a video of her — also sleeping — on my phone. I let the love for this tiny creature wash over me, and I waited. I watched the pump, minute after minute, but the milk came slowly.

My home became devoted to the cause of increasing my breast milk. I have eaten bags of lactation cookies. I have consumed more oatmeal in more recipes than I could have imagined. I have even tried to drink Guinness, which I’ve never enjoyed. I have taken supplements and prescribed myself an anti-nausea medication that has the side effect of increasing the hormone responsible for milk production. And I make milk. I breastfeed. But in the past months it has become clear that for whatever reason, I will never make enough milk to meet my child’s needs. And I know, rationally, that this had nothing to do with love, that supplementing with formula is more than OK. But still.

The symbolism here is almost too clear. For all the pressure I have felt as a doctor or a writer, there is nothing that compares with the expectations placed on mothers. We are supposed to fall in love with our babies immediately, to experience motherhood as a transcendent state. We are told to breastfeed for up to two years, as though that is a reasonable thing to expect, as though everyone’s lives and bodies can accommodate such a mandate. If we feel ambivalence, about breastfeeding or about the ways our babies have changed our lives, we are not to admit it.

But that is not the only way to be a mother. For those of us making the complicated decision to have a child later in life, there is inevitably something lost even for all that is gained. There is unimaginable joy and with it, the alternate life we will not live. I increasingly believe that it is possible to recognize that and to love even more strongly for the knowledge.

It has been three months and despite my fears, the ambivalence of my pregnancy has given way to a love that is so overwhelming it sometimes makes me want to cry. When I see my daughter’s little clothes around the house or she smiles at me or splashes her feet in the bath, she breaks my heart open. She is so small and so vulnerable.

And at night, when she wakes up, there is no more thrashing and flailing. I place her under my chest, her warm body close to my heart as it was for so many months, and she feeds. I feel her own chest rise and fall, listen to the sound of her breathing and watch her little toes wiggle in delight. I know that the milk might not fill her, and so she will have formula later. I am OK with this; there is value here that cannot be measured in ounces. And knowing that I am not the sole source of her nutrition is what allows me to relax, to take these moments with my baby for what they are. Not exactly as I expected, nothing ever is — not family, not motherhood — but something beautiful.

Maybe that is what it is to be a mother, to create a family: to hold your child tight while you feed her, even if that food does not come solely from your own body. And to know that, too, is love.

Daniela J. Lamas (@danielalamasmd), a contributing Opinion writer, is a pulmonary and critical-care physician at Brigham and Women’s Hospital in Boston.