Welcome to Mayo Connect! I can certainly understand your concern over these symptoms. To begin with, please note that a lot of neurological disorders are not properly diagnosed until many years after the symptoms appear (this would include MS and PD) and rare neurological disorders might take a lot of investigation at top-notch medical facilities. Therefore, you need to keep persisting to get a diagnosis and to seek the best neurological care you can find.
Do you live near a multi-disciplinary medical center like a university medical school or a Mayo facility?
I feel a bit confused about a doctor saying that the "white spots" were related to aging, given that you are only age 43. I'm guessing that the MRI was done of the brain, is that correct or was the spinal cord included in the MRI? As, @barbbie, mentioned a more thorough neurological workup needs to be done as you investigate these symptoms.
I had early onset PD without the typical symptom of tremors, so it was hard to diagnose as well and I went over 15 years with the symptoms before the diagnosis became more evident. So I would encourage you to seek out a top-notch medical facility, to research a great deal about neurological disorders before you seek a second opinion, to write down all of your symptoms and their frequency. Be sure to include when they were more likely to occur, i.e, at night, after exercise, when you are tired, stressed, before or after meals, etc.
Check out the website for the MS https://www.nationalmssociety.org/What-is-MS and subscribe to their emails, you will learn a lot. Do the same for the Parkinsons's Foundation website and also the Michael J. Fox organization. They will all provide you with weekly and/or monthly emails and you will learn a great deal.
I'm looking forward to hearing from you again. Will you provide updates as to how you doing with your search for a diagnosis?