I echo Cheshire Cats suggestion and, from a personal situation, what you say regarding doing the opposite to what is asked,is exactly our situation. I would ask for a referral to a memory clinic asap.I experience this, doing the opposite,many times a day with my OH.
Get it sorted with a CT scan which can rule in/ out some conditions. OH had a CT scan which ruled out AD. If you do have memory problems associated with Parkinsons, then the sooner you start medication, the better.
Don't delay. My concerns were ignored for years and the medication might have helped if prescribed sooner.
Surely, not knowing, and worrying is far worse than knowing and dealing with it?