Yes. Sorry.
I had a baby when I was 20 and I really wish I had waited. I am 27 now and TTC #2 and it's worlds apart and I feel quite sad for DS.
There is no rush! Enjoy life a little. It's not all about clubbing and stuff either. I never really liked that kind of thing myself. But if I'd waited longer then I would have been all the more secure in my relationship (not saying you're not, but I wish I'd stuck to my original plan of 2 years before engagement, 5 years before children), we would have had more time to save and work up etc. When you're 21 it really feels like you've been an adult for a while now but looking back 7 years later, I'd barely really got started and I feel like I actually missed a big part of the parenthood "experience" which is that shift, because I never really got to appreciate/properly experience adulthood before becoming a parent. It's partly the freedom to mess about a bit with employment, try different things, knowing if you really screw up financially it's not the end of the world because it's only yourself you're supporting and there's likely a safety net, being able to travel for work for a year or two or at a moment's notice without having to think about childcare. And it's partly working out who you really are and what you want - from life, in the way of a family (I certainly have different ideas now), from relationships, where you want to live, etc. I felt like by about 25 all of that was beginning to come together. Hindsight is one of those annoying things.
I agree about the idea of concentrating on a wedding first. I didn't want a fancy wedding at all and I didn't have one and it was fine. But it would have been really lovely to have a honeymoon just the two of us. It would have been lovely not to be struggling for money and having to rely on family to help us, nice to have the freedom to save and make it our day exactly as we wanted even if we did do it cheaply. Plus, joking but seriously: The experience of planning a wedding together is pretty brutal and will give you an inkling about what it might be like to plan and carry out the raising of an entire human together. IMO, those kinds of tests are really crucial, because if you find out you're crap at compromising or it really hurts when they go behind your back and do something or that they are likely to pick the fun bits and leave the boring stuff to you, or their family is insane and controlling, or how you react when he accidentally pushes your emotional triggers or whatever it is - it's better to find that stuff out before you have children, because then you can decide if it's make or break and you also have the energy and the opportunity to actually address issues which come up, now, before the decision is going to affect your child's life, rather than trying to address things which come up for the first time when you're hormonal and emotional and sleep deprived and you feel like the baby has stolen part of your brain.
It would have been nice to go on holidays as a couple before having DC. I didn't ever really get to do that. And financially once you have DC your finances are always stretched and the cost of everything goes up - it would have been a great idea to both have the money to invest in things like a decent car, furniture, house, holidays (memories, relationship building) etc before having DC, rather than trying to buy those basics after having them, when you're stuck with cheap options or go without, and also build up a bit of a savings buffer so that if we were struggling we'd have something to dip into.
Having DC young is in many ways just as wonderful as having them when you're older, and it definitely isn't a life ruining event but you're also compromising on a lot of things which can just be hard. I was just old enough not to have much in common with the teen mum crowd but young enough to be worlds apart from the first time mums aged 25-35 with careers and mortgages and husbands. None of my friends had children at the same time as me. So it was actually really isolating at times and I feel quite envious now of friends who are just having their first because it was a different experience for me.
Just some thoughts. When I was younger I would have said yes 21 is OK but with hindsight - I don't believe it is and so my advice would be to wait. Your DP isn't going anywhere, your fertility isn't going anywhere. The broodiness, yeah, that might not go anywhere either but you'll have a much better experience I reckon by holding off than if you jump into things.