Daughter's stomach

  My 16 yr old daughter has always had a sensitive stomach(too much junk food or nerves upsets it).  Since she has started having periods, she gets nauseated the first couple of days.  Sometimes she vomits and sometimes she just feels like she could.  I have had bloodwork, etc done on her and everything comes back normal.  The Dr. thinks it might be like a migraine,but in her stomach and not head.  He wants to continue to test, but it is getting very expensive.  He gave her Donnatal and it seems to help.  Could you give me any more info on this?  Do migraines occur in the stomach and should I continue to put her thru testing?  She is missing too much school and I need to try to resolve this.  Thank you.    
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Dear Julie,
Thank you for your question. Abdominal migraine can present with symptoms of abdominal pain an/or vomiting.  Headache and the