I keep experiencing dejavu, accompanied with a feeling of fear, and like i'm losing a grip on reality. starting to happen several times a month. i'm starting to think i'm losing my mind. i'm 47, have pmf and have chiari, and had a stroke?

Not feasible to be fully accurate, but one might consider the "deja vu" episodes could represent auras secondary to Complex Partial Seizures. Other etiologies could certainly be considered, and a visit to your doctor plus an EEG might clarify. In meantime, do not drive, operate power equipment, do activities at heights, or swim/ bathe alone, until this is convincingly diagnosed.