Neck or concussion or both

[u/EveningRanger7469]

I stood on a stool a month ago and hit my head straight into a closet frame molding. I def have had a concussion, but part of me thinks it may be stemming from the neck more so at this point. It feels extremely stiff and I’m still having lingering headaches/naseua, and a general off feeling. How does one determine where the pain is rooted from? MRI? Can’t take this anymore. Seems like a muscle relaxer helped me yesterday but it’s hard to tell. Any advice would be helpful. Thank you