Migraines associated with stomach pains

Hi-

My son is 18 years old, he has been suffering from migraines since he was about 11.  He gets nauseous, his stomach hurts and some times his body is paralyzed where he can't move.  He has had just about any test that you can name.  I have even taken him to a gastronologist, befcause he also has diarrhea at times.  No one has been able to help him with his problem.  Now he is in college and when he gets a migraine it keeps him from going to class.  The school is aware of it.  I would just like for him to get some relief from this.  Does anyone know a doctor that specializes in this.  Please let me know.  Thanks for your help in advance.