My best friend is pregnant, and I'm not sure we can be friends anymore.

For our whole lives, my best friend and I have done everything at more or less the same time.

We started school together. We learnt to read together.

Once, I beat her in a spelling test by a single mark. The word she got wrong was “of”. I was chuffed.

She cried.

I remember the moment distinctly because it was one of the few times in my childhood that there was any difference between us at all.

Throughout school, were inseparable. We had crushes on the same boys. We made the same friends. We had the same hobbies (netball, writing stories) and asked for the same things for Christmas (horses, One Tree Hill DVDs).

We fell into long-term relationships at similar times in high school and ditched our boyfriends just in time to start university together.

We enrolled in the same course. We made the same friends. We planned our futures: European travel, fancy jobs, the apartment we would live in and furnish perfectly.

(We were both in relationships again by this time, but boys are notoriously bad at interior decorating.)

That year, our new friends mixed us up more often than not. We answered to each other’s names.

We’re practically the same person anyway, we joked.

We talked about everything: love, loss, the existence of God or lack thereof. We shared secrets like they were skittles. We made grand plans and discarded them and started again. We weren’t in any hurry.

Then, a month ago, my best friend told me she was going to have a baby.

It’s the first thing we haven’t done together since we met at six years old.

I was so shocked I thought she was joking. I forced her to repeat herself three, four maybe five times.

She wasn’t asking for my advice – she was stating a fact. After weighing in on every decision she’d ever made, from where to go on her first ever date to what lipstick colour looked best on her, I’d been left out of the most important one.

None of our other friends could see what all the fuss was about. They congratulated my best friend at length, shedding tears and sending flowers.

Apparently, I was the only one who was left reeling by the news.

It’s not that I’m not happy for her. I am, painfully. But the happiness is tinged with disappointment that our friendship, as we knew it, has changed irrevocably.

I’m jealous. I hate the thought of us not being in the same place, doing the same things. I don’t know how to navigate this new landscape.

Watch the Mamamia Team’s last texts from their best friends…

Recently, she asked one of her other friends to organise her baby shower. I found out over text. We don’t see each other in person so much anymore. She’s working extra hours now, saving for the baby.

“It’s only because you’ve never been to a baby shower before,” she texted me.

And that’s the problem: I’ve never done anything remotely baby-related before.

I don’t even know how to act baby-related. A few days after she made her announcement, I texted her, “Have you actually THOUGHT about breastfeeding though? Isn’t that TERRIFYING?”

She never replied. I later heard from a mutual friend that, in her words, I “wasn’t taking the news seriously”.

When we do talk, it’s now at cross-purposes.

She’s immersed herself in a world of prams and cots and I’m watching Making A Murderer on Netflix.

I’m impulse-buying leather jackets and holidays to Fiji and she is growing a new life inside her uterus.

The night before she told me about her pregnancy, I got drunk, fell over and skinned both my knees like a child, and she is preparing to give birth to a child.

Last week, we met for coffee. Slipping into the old routine, I relayed a fight I’d had with my boyfriend at length. This was the part where we normally dissected every word.

Instead, she just smiled a tight-lipped smile.

“My boyfriend and I hardly fight anymore,” she said. “I think the baby really puts things into perspective.”

I know this is a time when she needs support, but I don’t know what support to offer.

I can feel her drawing away from me. I’m subconsciously avoiding spending time with her.

All those years ago, when she misspelt the word “of”, the problem was easy to fix. The gap between us could be closed with a simple explanation: “of” is spelt with an “f”, not a “v”, although it doesn’t sound like it.

The gap between us now isn’t patched so easily. We’re no longer on the same spelling list. We’re books and books apart.

I don’t know how to catch up.

After nearly two decades of friendship, I think it’s time for us to break up.