subarachnoid hemorrhage

About 5 yrs ago I was home when I actually heard and felt a pop sound in my head, within 2 seconds I had the worse headache ever.  I couldn't see, was sick to my stomach and became very disturbed.  My husband took me to a local ER where the doctor had me squeeze his fingers, listened to my heart, checked my eyes and then diagnosed me w/ a migraine.  He gave me a pain med (can't remember name) for migraines.  It took me about 4 days to start feeling normal again.  About a week and half later my reg doctor gave me a CT scan w/ dye.  It came back normal.  I have suffered memory loss since, scary memory loss.  However, Alzheimers runs in my family and so I thought it may be normal progression of that.  The story just came out about Brett Michaels and all I could think was this is exactly what happened to me,  He was diagnosed w/ subarachnoid hemorrhage.  Could I have been misdiagnosed?  Would the scan show such hemorrhage so many days later or would it show it today?  If my memory loss is do to this, could it be fixed?  Any info would be greatly appreciated.