This is VERY serious: pls help! 2 y/o grandson "gags" constantly?

then throws up...when he smells/looks at food..he's always done this..Dr. prescribed Prilosec which is NOT working..now suggests chest x-ray (possible for a 2 y/o?) Vomits all medication.... Today Dr. gives nebulizer...I have suggested a pediatric gastro specialist...we're in S. E. North Carolina...ANY REAL speculation is appreciated!