This is Dr. David
I am sorry he is having nausea and pain below the sternum.
this could be due to too much stomach acid in the stomach.
you can try over the counter acid blockers like prilosec and nexium and zantac and see if these help decrease stomach acid and help his symptoms
but since he is 2 weeks post op, you really should bring him back to see his surgeons next week or see his primary care doctor soon to be evaluated to see if he might be having complications from his surgery.
he needs to be eating bland food like a BRAT diet of toast, rice, applesauce and bananas and chicken broth
he needs to avoid alcohol, spicy foods, fatty foods.
when can you get him in to see his doctors again?
he could have a stomach ulcer possibly from steroids or pain medications used during his surgery.
some doctors would recommend him to go to the ER to see a doctor right away.
let me know if you have questions.