What age do you think is considered old age?ㅠ

Hello!!!
I am a working professional in my 30s.
Lately, I've been thinking a lot about marriage and childbirth. Especially, the word 'advanced maternal age' keeps lingering in my mind.

I have been working at a company since my late twenties. I found the work interesting and achieved good results. As a result, I suddenly find myself approaching my mid-thirties. I am seriously considering marriage with my current boyfriend, but I occasionally feel a wave of anxiety.

Recently, I went to the obstetrics and gynecology department for a check-up. The doctor told me, "Since you're of a certain age, it would be best to start preparing for pregnancy as soon as you get married." Hearing those words, my heart sank. I knew in my head that pregnancy could be risky at my age, but hearing it directly from the doctor made it feel all the more real.

Looking around, younger friends than me are already having children and busy with parenting. Just opening SNS is filled with baby photos, and when I meet friends, we blossom with talk about parenting. I secretly envied hearing those stories, but at the same time, I thought, 'I'm not ready yet.'

Many colleagues at work are also facing similar concerns. Recently, a team leader I work with had her first child at almost forty, and she has been receiving special care from the early stages of pregnancy because of her advanced maternal age. Seeing her, I also think I should prepare before it's too late...

I also shared these worries with my boyfriend. Fortunately, he understood and said, "Let's take our time and prepare slowly," but my inner anxiety still remains. I feel like a year will pass quickly once we have the wedding, go on the honeymoon, and get used to our new home.

These days, watching videos related to pregnancy and childbirth on YouTube has become a daily routine. Once I started searching, the algorithm became quite intimidating lol.
Listening to the experiences of pregnant women over 35, I find comfort and gain information. Fortunately, medical advancements have made healthy childbirth possible even at a later age, but still, a part of my heart feels heavy.

When I confided in my mom about these worries, she said, "These days, what’s considered late at thirty-three?" But right after, she added, "Still, you should have a child soon," which makes me think that deep down, she’s also quite worried.

Sometimes I wonder, "Was I too selfish?" Did I miss something important while only thinking about work... But on the other hand, I reassure myself, "The path I've chosen so far isn't wrong." At what age do you think the age of a late bloomer begins?ㅠ