Anxiety disorder(s) and multiple sclerosis (MS) are two completely different diseases.
Multiple sclerosis is a neurological autoimmune disease wherein the immune system attacks the myelin coverings of the nerve tracts in the brain (white substance). Lesions in the white substance can develop at any location, so the symptoms MS differ according to the localization of the lesion. Lesions can be repaired but not completely; other lesions develop in time. That’s why some symptoms are relieved for a while but then other, new symptoms appear. Paralyses, loss of balance, disordered movements, loss of senses, dementia etc. are all symptoms of MS. Multiple sclerosis is chronically progressive disease with a bad prognosis. An MRI can detect the brain lesions in MS.
Anxiety disorders (neuroses) are psychiatric diseases. There are many types of neuroses: anxiety/panic, phobic disorders, depressive, somatoform disorders (hypochondria), conversive disorders (hysteria)… Typically, somatoform disorders (hypochondria) can imitate any other organic disease. Patients feel the symptoms of diseases; but they are not real; the diseases only exist in the minds of the patients.
Because your MRI is OK, it seems likely that you are suffering from somatoform disorder (hypochondria). Doctors typically prescribe Xanax (alprazolam), to treat neurotic disorders (like hypochondria) not MS.