Don't mourn for the past - think about what it is you want, now, that you don't have. I'm guessing that Cote may have it, you know. I think your intuition is telling you that you want another, different, partner, or at the very least, the relationship you two have needs changing.
You also sound as though you want to extend your friend circle and your social life. You can do all these things, even though you have a 6 year old. It will require a conscious amount of work, though. And that's OK. Think about all the things you put effort into (housework, home deco, shopping, gardening). The same effort, not necessarily vast amounts, but small and regular, needs to go into this area of your life that needs a bit of gardening.
It probably won't ever be the same as when you were younger but a. most of the people you meet now, who are your age, with children, will be in a similar boat b. you have some of the things that you yearned for in those earlier years c. you are older and wiser, which is part of why you don;t try and recreate the "you" of those past years now - you have to embrace that as a good thing - even though it does mean losing stuff.
I really empathise with how you feel, though! There are many times I could kill to just waltz out of the house , just because I feel like it, without having to plan and calculate ... and pay! And that lack of freedom to just go out does wreak carnage on your social life. So it's not just you.
But I do remember that a lot of those child-free years were years when I was younger, more anxious, more uncertain. And a lot of that time was spent searching for who i was, and what I wanted. And therefore I spent an inordinate amount of time doing things that, actually, I found quite boring. Shame really. But all part of that journey of discovery. Oh, how the older, wiser, more encumbered me gazes into the magic mirror of time, looks back on younger me and says things like: "Don't bother going to that party. You're going to be bored witless, a really unpleasant person is going to drunkenly corner you, and you're going to be too polite to extricate yourself, even though you are fuming inside. Spend the time with "y" instead - you like that kind of thing." But that, of course, is the wisdom accumulated having done the journey.
So, you are where you are now. If you went back in time, it really wouldn't work, in so many different ways. The trick is to work out what it is you want to change, or add to, in the present, and see if you can work towards that, even if it is going to be hard work.
Good luck. I'm sure you are not alone feeling like this.