Elizabeth,
Migraines usually begin before 50, but CAN start at any age.
Waking with a Migraine is often an indication of a sleep problem. If a nightmare disrupts your sleep, it's possible that that kind of disruption is a trigger for you. Many sleep issues can be a trigger -- too much, too little, disrupted, or poor quality sleep.
I wish I had better answers for you, but anything more definite will need to come from a doctor who can review your medical history and examine you. If you need more help than your current doctor can give you, please don't hesitate to get a second opinion or see a Migraine specialist. Take a look at the article Migraine and Headache Specialists - What's So Special? If you need help finding a Migraine specialist, check our listing of Patient Recommended Migraine and Headache Specialists.
Good luck,
Teri