I got a moderate concussion 3 yrs ago and my headaches are where i got hit. i have trouble remembering things and can't think as fast. any ideas?

See a neurologist: Have u had those symptoms x 3 years? Or had they appeared now? If they are anew , I wouldn't relate it to the past concussion.They would require a neurological eval .Important to get more information and likely an MRI to R/O a structural lesion - If you had those symptoms x 3 years already and gone through testing and neuro evals without response, a psychiatric evaluation would be in order.

Neuropsychologist: I think you are suggesting that your problems in memory and thinking speed have persisted since the concussion. If that is the case, then a neuropsychologist would be the professional to consult. If they are more recent, then you need to consult a neurologist.