Hi, Ryebecca! In addition to the great articles that Meaghan suggested, I'd like to add Tammy's great article Rethinking Exercise.
Have you considered yoga and Tai Chi offer lots of upper-body strengthening with very little impact and the benefit of increased flexibility? Don't forget to check with your doctor before changing your routine.
Thanks for sharing your thoughts and experiences with us! -All Best, Donna (Migraine.com team)