R.J.
Not alone! In fact, I've felt/acted pretty identically to how you describe for 8 and a half of the past 9 years.
I've become a bit more relaxed fairly recently, since my son got sick. With a very real chance of him dying these past few months I had to come up with a "plan". Technically I have 2, since I can only imagine my headspace. Without going into details, he dies, I die. I don't want to live without him, and I'm officially choosing not to. Not that I'd tell anyone that outside of cyberspace. But I'm ready. Lawyers have drawn up all my papers so everything goes to whom I want it to go to, my affairs are all in order. I'm good to go... whether it's plan A or plan B.
We're home now, and things are going fairly well. But I've found that an unintended side effect from plans A&B is that I'm no longer as lost when he's elsewhere with other people. Which is totally WEIRD. I keep waiting for the fear and 10,000 possibilities to stream through my head, but they don't.
As always, not recommending others do this, just I what I did.