Post concussion problems

I’m new to this blog and am excited to maybe get some answers. I was in a bad auto accident 3 yrs ago. We were t boned by a car going 65 mph. I suffered a bad concussion and stiff neck. 3 years later I still have daily tinnitus, headaches, trouble focusing, irritable, and yesterday I was nauseous, headache and trouble focusing, just as if the concussion had just happened. How do I deal with all of this?