What Causes Vomiting After Eating Food?

my husband started vomiting on 11/18/17 anywhere from an hour to 8 hours after eating. He was diagnosed with graves disease in 2013 and had radiated iodine treatment to kill it of and is now taking levothyroxine 125mcg daily. he went to the doctor on 11/20/17 and they pulled his thyroid panel which came back fine was told he might have a virus. he has never ran a fever or had diarrhea. he went to the ER last night and they ran blood work,urinalysis,and a ct scan of his abdomen which all came back normal. He still continues to vomit. he was given a rx for suclurfate and prilosec which he started taking today but this morning after taking a shower and getting hot he started vomiting again. so far he has been able to take the meds after that episode and has been able to keep some crackers and chicken an rice down,but he has not gotten hot since then. the ER dr seems to think that he may have an ulcer. could this have started the vomiting suddenly and it continue for a week now. should he be seen by a gastrologist to determine the cause of his illness.