Ah, no worries! I came on this section to be honest by accident as I meant to click on LGBT children (eldest DD mentioned above is pan sexual, at 25 she’s one very confident and secure in who she is woman but had rough teenage years so I occasionally go on that section to share what helped us).
You’d obviously rather not have your Ex’s involvement so before anything else, I’d check your legal position. I suspect she has rights but find out what those are. If she does want to exercise them then yes she has to be paying maintenance, end of - you may not want her money but stick it in an account for your DS. You never know, it may put her off!
When DDs father re-appeared 2 years later wanting to play Daddy, I’d have cheerfully seen him under a bus! Yes it’s bloody awful to sit down and be grown up but if she’s determined and legally you’ve got to, strap on your big girls pants and keep the discussion civil. It’s got to be all about the welfare of your DS and how this arrangement works best to suit him. I would make it crystal clear that if she wants to be involved in his life then she has to commit to being in for the long run, it’s not something she can run away from.
Completely understand the mourning of the life you thought you’d have - I remember feeling quite devastated pushing my pram around in the park on my own surrounded by happy seeming families. But absolutely it gets better. I’m very close to my youngest DD but we have a very different relationship than the one I have with eldest DD - it felt like her and me out to conquer the world for the 10 years I was a single parent! You yourself become stronger as well. Another added benefit is that you’ll get to call the shots on the important things in DS’s life - discipline, schooling etc without having to make compromises to someone else’s opinions.
I do miss much of this period in my life and honestly, the sadness does fade and there is much in the new reality that is very good. I would 100% recommend removing anything that reminds you of your ex from your house, your phone, your laptop etc. Give anything you don’t want to chuck to a friend for safe keeping. A clean out of your life together does help mentally starting afresh!
Good luck! Sorry if there is a lot of waffle in both messages.