I could have written this myself (even down to the username, what a song).
I'm 31 and leaning heavily towards not having kids right now, and I have friends with 10 year olds and their first on the way and all things in between. A fair few that are pregnant now are saying the same thing about not wanting to be 'too old', and as someone whose parents were young when they had me (and I liked that, for various reasons)... it all feels like a lot of pressure. And my own MH is a balancing act and one I'm currently balancing okay for the first time in a decade - I feel like throwing a baby I'm ambivalent about into the mix would basically be a hand grenade into my brain right now.
Also, I just don't want one right now (or probably ever). In fact, the people who have small kids now are putting me off even more - it looks relentless and exhausting. I think I'm old enough now to really see what an undertaking it is compared to when my 20 year old friend had a baby and it seemed like an interesting novelty.
What I really want is someone to - yeah don't have them, it's great. I have nobody around me who affirms the other side of the coin, just lots of people assuming I'll go one way. And that makes me feel like there's something wrong with me that I'm not sure/leaning away from it.
So instead, I've told myself it's fine.
I told my mum to simmer down or we'll just get another cat.
If friends ask, I say I'm too busy being the fun aunt (or if they're really rude or pushy, "God no, I can't stand children" so they do the shocked Pikachu face).
If I waver and suddenly get the urge to remove my coil with some pliers (thank you, hormones), I remind myself I like my life, I like my job, I've got plans that aren't kid-friendly, I don't want pregnancy or a newborn, I resent having to water plants never mind raise a human, and you can't get shitfaced on tequila on Christmas morning if you've got a baby, and it goes away again.
That's not to say I won't change my mind in a few years, not naive enough to think that, but I think a lot of my turmoil at the moment has been because I feel wrong for not wanting it, not that I'm unsure either way. So I'm giving myself permission.
People have kids much older than you are now. Some of them never do. Neither choice is wrong, so don't worry about that - surely better to have a child at , say, 35, that you are ready and excited for than one at 31 that you're not ready for and not sure about.