There was another thread on this recently and I thought this advice from @bertiebotts was brilliant:
I had a baby when I was 20 and it wasn't the right thing to do.
The main problem was that I lacked the life experience to really evaluate my relationship critically - and it wasn't a healthy one.
This is the most important thing IMO. You can change your living situation, job, income, you can't retrospectively change who your DC's father is and it's hard when you only realise later that you got this wrong.
It's also been harder than I anticipated being "out of step" with all of my friends - most of my "mum friends" are 10 years older than me!
But the relationship thing is the most important. Ask yourself these questions - and ask them honestly, even if you never voice this to anybody else.
Do I feel 100% equal in my relationship, or does it feel like one of us is the "driver" and the other the "passenger"?
Is our situation legitimately shared, like a family, we pool resources such as time, money, emotional energy, earning/career potential and understand there's an ebb and flow to life events, or does it sometimes feel like we're two people living separate lives side by side, or there's a push to make everything artificially "equal" at all times such as splitting out bills down set lines?
Do I like and respect his family, or do they make me feel anxious or insecure?
Am I sexually satisfied in this relationship or does it often feel unbalanced?
Do I feel heard and respected when we disagree? Are we able to have discussions respectfully? Or does it often feel like issues are left "on the back burner" or unaddressed, sometimes repeatedly?
Does he encourage and value and push me to be my best self or is he seemingly content with where I am, even seeming to want to keep me here?
Would he make personal sacrifices to support me or would he resent that?
Am I able to be myself around him or am I ashamed and hide certain aspects, or save them only for other people?
When I am vulnerable (e.g. ill, grieving, extreme stress) does he take care of me or does he act as though this is my problem? (And is there a difference in expectation when this is reversed?)
Have we experienced a complicated project or event together, such as planning a large party like a wedding, hosting an event like Christmas, or buying/choosing and decorating a house? Particularly where emotions run high and clashes are likely and especially if combining family traditions must be navigated. Do I feel that we make a good team for things like this, or is it something that I dread?
If it's not clear, the first scenarios are good, "green flags" for starting a family with somebody, the second scenarios after the "or" are warning signs or "red flags" - if you've got one or two and there are specific reasons for this and you know how you'd handle them as a couple, that might be okay. If you're finding you tick a few more or you can't really answer why they are or you believe that these are normal parts of a relationship, hold off for several more years. Often these "red flags" can feel totally okay when you're both young, healthy and independent. That a baby changes that dynamic can be unexpected, for everyone. But these are the kinds of things which tend to magnify and bloom into real difficulties once a child is in the picture. The last two refer to events which you may or may not have experienced together. It would be useful if you have experienced something like this prior to making the decision to have a child because having a child is a combination of these two things and having it be the first experience of such an event can be catastrophic if you don't know what to expect from each other.