Grief and loss are some of the most natural painful feelings that there are. Natural because loss is unavoidable, grief is something all human beings will encounter at some point, and hopefully learn to manage.
However, with any painful emotions, our responses that naturally protect us from pain - what therapists call "defences" - can sometimes cause other problems.
As you've spotted, you've got a bit stuck. Not just with the difficult emotional task of letting go of a past relationship, but the even more challenging version - doing the emotional work of changing a marriage into a co-parenting relationship.
If it's any consolation, I believe this is one of the most difficult tasks for grief because we can't simply make a clean break, like with a more simple break-up. And of course, death sadly leaves no option - we never see the other person again.
But with co-parenting we have to keep relating, and that makes it extremely hard.
I encourage you to understand the desire to know "what she's up to" as the enemy here.
That's your attachment system reacting as if you're still together, and by doing so the anger and annoyance can feel like betrayal - even though it's not because you're not together.
But as natural as these feelings are, they block the experience of the emotional processes needed to allow grieving and moving on to happen.
It can be less painful to feel anger, directed at another person, than to truly accept the relationship is over and allow space for the sadness.
And while it's generally true that we can feel anger in the place of sadness, it's also a particular problem in the context of a break-up. The anger - and the resultant focus on your ex-wife - essentially keeps the relationship alive, at least emotionally, for you.
So genuinely accepting that the relationship is over is hard, but can be helped by taking specific action.
Firstly, you need to work on disengaging as much as possible. That means not doing anything outside of engaging for genuine reasons to do with co-parenting. It also means starting to work on noticing when your thoughts drift to angry or jealous thoughts, and distracting when your thoughts go there.
It can be a good idea to disengage on all social media and even block if that helps you not browse her timeline to see what she's doing.
And as tempting as it can be, resist the urge to lead conversations with the kids in ways that mean they tell you about her private life.
All of this might at times be challenging and painful, but that pain serves a purpose. To truly move on we have to go through it - it can't be avoided.
But you don't have to do it all at once. And you do get to be gentle with yourself. But if it's too hard, or too distressing, then that can be a sign that you may need some help - from a therapist or counsellor - to process the change.