Don't know if this will be helpful, but just came across this while doing research.
" Stomachaches or Headaches. No one knows why stimulants cause these problems in some children and adults. But often it’s helpful if the patient eats something before taking the pill. If the problem persists, it may be necessary to try a non-stimulant medication."
No, that would be unusual. If the migraines started soon after you started the Concerta, then there might be a connection. But basically, Concerta is out of your system after about 8 to 10 hours. Anxiety is a common co-disorder with ADHD and that might be more of the problem. Are you on any other meds? How long have the migraines been going on? Anything else happen during that time period? What do you take for migraine relief?