Hi and welcome.
It's difficult to say if this is PCS or something else, although the symptoms you describe are consistent with PCS. It just seems unusual that these symptoms would spontaneously start a couple of years after the head bump, but the brain is a complex organ and just about anything is possible.
Regardless of the cause, you do have symptoms to address. You may want to see a clinical neuropsychologist for a neuropsychological assessment. These can be expensive but if you have health insurance it may be covered; if you are seeing a neurologist or physiatrist they should be able to provide a referral.
In addition to this site you might visit the Brain Injury Association for your state for general brain injury information and specialists in your state.
http://www.biausa.org/state-affiliates.htm
Best to you, let us know how things progress.