08/27/2014 08:16 pm ET Updated Oct 27, 2014

MISSING: One Bunny Boy

When people find out you're pregnant, advice flows freely from their mouths. Every new mother hears about diapers and baths, pacifiers and baby bottles. We get conflicting information about nursing versus formula, family beds versus cribs, and store bought baby food versus homemade, pureed sludge. It's enough to drive us all a little loony, but we are thankful for the advice of seasoned mothers. At least I was.

Until now.

Earlier this month, I officially became the mother of a teenager. As I readied the house for the party, cooked food like I was making Thanksgiving dinner solo, and swore over the homemade butter cream frosting melting off his cake, I had very little time to reflect on the enormity of the day.

Not one mother ever warned me about the lull I would face in the wee hours between preparing for a thirteenth birthday party and the actual event. Because my son is one-fourth of the nerdiest family in America, I spent the hours after the cooking hanging Dr. Who posters on the walls, affixing a giant TARDIS poster on the door, covering the tables in royal blue tablecloths and hanging TARDIS lights. (TARDIS stands for Time and Relative Dimension in Space, a twirling British Police Call box that Dr. Who travels in, for those of you not in the know.) As I sat down to admire my work, I noticed the pile of pictures I had yet to tape to a board.

On top was Jimmy's first picture, a slightly jaundiced stick of a baby born six weeks too soon and fast asleep for his first photo op. In stark contrast, the next photo shows a beet red Jimmy visibly screaming at the top of his lungs, looking for all purposes like I'd just dipped the child in lava instead of putting him in nice, warm bath water. Next in the pile was my Easter boy, a nine-month-old baby in a hooded sleeper complete with little white bunny ears. Then there was the one-year-old hambone I called my son, grinning for the camera with birthday balloons adorning the background.

That's when Jimmy ran down the stairs and stood before me.

That's when I started to cry uncontrollably.

Where is my bunny boy? He's been replaced with this teenager, shadows of his former self lingering just behind the newly formed shades of the man he will become. Above his lip is the dark peach fuzz that I'm not ready to believe will someday be a mustache. Covering his milky brown eyes are the glasses he picked that he thinks make him look like David Tennant's version of Doctor Who. His feet are three sizes bigger than my own. He's a full neck and head taller than me. This beast that's rumored to be my son has grown man legs, covered in hair as thick as his dad's.

Gone is the little guy surrounded by frightening grass, his world limited to the well-defined borders of the blanket upon which he sits. Gone is the little boy who had me read the book Zelda and Ivy so many times that it literally fell apart. He's no longer sticking his arm into the paint bucket all the way up to his armpit. He isn't taste testing the dish washer fluid and already knows the danger of swallowing a quarter.

Before me stands this strange concoction of hormones that has my little baby's voice sounding more like his father every day. I miss the way he used to sigh just before he fell asleep, and how often he told me he loved me. He's too cool for that now, too big to show his mom he still cares.

I cry because I've got five years left before he becomes an adult. Five short years left. It hardly seems enough.

As I sat there, bursting into tears, sniveling and snorting like the mess that I am, he came over to me.

"Mom, what's the matter?" he asked.

"You're growing up," I somehow managed to get out between gasps for air.

"It's what I was made to do, remember?" he said to me.

No, I think to myself. All those well-meaning mothers with all their time-tested advice neglected to let me in on the pain that is mothering. How many mothers told me when I was pregnant that one day I'll turn around and a half-formed man will be living in my house and my precious baby will be missing? How many mothers told me that the day will come when I can't coax him into bunny ears for a picture even if I promised him unlimited video game time? How many mothers told me how much my heart will hurt when I realize my baby simply isn't a baby anymore?

None. My sisters-in-arms left me in the dust to figure it out all alone.

I am left to find solace in the one thing left as proof that Jimmy is the baby I've raised all these years. He still squawks every time I tell him to take a bath, like he's some kind of human-chinchilla mutant that only gets clean by wallowing in dirt. The next time he fights me about showering, I'll argue back with a smile instead of a scowl, hanging onto the only inch of my little boy I have left.

This blog post is part of a series for HuffPost Moments Not Milestones, entitled 'The Moment I Stopped Being Perfect.' To see all the other posts in the series, click here.