What Causes Discomfort Muscles In Neck Area Post Head Injury?

hi I fell about 2 years ago hit the back of my head pretty hard since then I ve had problems with my neck muscles some times when I put my head down I can feel the muscles in the top of my head pulling I ve went to several doctors and they assume I have parkancins or how ever you spell it I know how people look when they have that so I don t know how they can assume it s that could it be a pinched nerve I just started taking diazepam 10 mil and it helps alittle but when I take 2 I feel almost 100% what do you think about the piched nerve?