After 4 week really bad spell of ongoing visual disturbances and constant severe headache been diagnosed as a flair up of my chronic migraine . my question is , is it rare to have an ongoing severe headache for so long and still be a migraine ? scary?

Please see the Emergency room, an imaging study may be indicated. An uncontrolled migraine is possible and a Neurologist may advise treatment. Keep well hydrated, rest,ibuprofen is sometimes helpful. Watch for signs of dizziness, imbalance and please see acute care.

Your headache pattern is not at all atypical for emerging "Chronic Daily Migraine" patterns. This could be potentiated by use of analgesics, especially Tylenol, on a regular basis. Your neurologist could break up the pattern easily. Get proactive and engage in preventative measures, and make certain that a new co-morbidity has not emerged.