I stopped with one child for a multitude of good reasons, and I never regretted not having more. I have quite a few middle-aged and older women friends (I'm now 64) and we have talked for long, long hours about our families, our hopes and wishes and disappointments.
I have NO older friends who regretted, ultimately, stopping with one or two children. They did have to deal with "baby cravings" that came and went, and were sometimes very strong. (Thanks, Mother Nature!) I have several older friends who wish they had stopped with fewer. Not just one fewer, but sometimes two.
Every single mom who regretted one or more of their children loved them deeply and would never have given them up. But they would admit, maybe after a couple of glasses of wine, how very hard some of those pregnancies or infancies were/are on them physically and emotionally. A few of those kids had/have special needs, or demanding personalities, or physical handicaps, which have caused real heartache and stress in the parents for far longer than 18 years of childhood.
Most families who have even a challenging or unplanned child do manage to accommodate them happily and consider them a blessing. But based on talking to probably at least a hundred mothers over many years, the advice to "go ahead and have another, you'll never regret it," is simply untrue. I doubt that the women I talk to are maternally deficient – many of them have lived, or are still living, lives of ongoing sacrifice for the sake of their children.
And then there's the environment that must support all of our children and their children, for centuries into the future. I know that lots of people believe the climate change alarm is some sort of hoax, and that we can go on living prodigally and making big families forever. But one of my reasons, way back in the 70's, for stopping with one child is that even then, I could see the effect on the Earth and on society of population pressures. The situation is many times worse now, but we tend to see only what we've always known, so if the world around us is already crowded, degraded and depleted, or if we live with low-level pollution or impossible traffic every day, we simply don't know how much better it was two generations earlier.
So, my suggestion is that you really consider whether another baby is a "must" for you. Real life has a way of changing our long-term hopes and plans, and you're wise to wonder about that before it's too late to decide otherwise. Whatever your future, I sure do wish you happiness.