When my daughter got her first concussion, we were told that symptoms could last up to six weeks (dizziness, nausea, ringing in her ears, headaches, concentration issues, etc.). Once the six weeks were up, then the official diagnosis of Post Concussive Syndrome was acquired with no defined standard time of recovery. You need to rest as much as possible and drink a ton of water so that your brain can heal. And be patient with yourself.
I hope you are feeling better very soon.