I remember feeling this way, it tended to be right before a recycle. We broke up and got back together many times. She mainly initiated contact but I did it too a time or two.
This lingering feeling haunts me and it comes back when I'm alone.
And this was why. I was alone and lonely. Are you feeling lonely? It's good to sit with this feeling now and again, then get out and do something. Are you involved with anything new or re-engaging with old hobbies? Sounds like you are touching base with friends? This feeling will pass, that's something I had to remind myself of many times before I was over the ex.
It gets better.