I have the same fear...
MS, neurologic Lyme disease, spontaneous intracranial hypotension.
They can all have similar presentations and for those of us who have worsening symptoms that include physical sensations like paresthesias, numbness, headaches, blurry vision, etc., the natural thing to do is worry about progressive disease processes. I have been assured and reassured by neurologists, neuro-ophthalmologists, headache specialists, and others that this is not a progressive neurological disease, but rather, an extreme form of migraine with persistent aura symptoms.
This doesn't put my mind at ease however, because who is to say this is even reversible. No medication or "tincture of time" has helped. The fact is, I develop new symptoms almost monthly and my existing symptoms just keep worsening.
Anyways, I do think it wise that you be evaluated by an experienced provider. I wish you luck and hope there isn't anything more sinister underlying your HPPD.