Been there with the first concussion and back there now. It's such a difficult thing to go through. Your "flight or fight" response is switched to "on" all of the time. It caused me a myriad of unpleasant (that's putting it mildly) symptoms, including insomnia, anxiety, depression, racing heart, no appetite, feeling disconnected, etc....the list goes on. It did get better over time after my first concussion, however, it was a slow process for me. I now find myself back in the same space and am trying to roll with it, but it's tough.
Remember you aren't alone in this!