I would stress to your oncologist that you are having such severe stomach problems, and tell him you won't do any more chemo until you get some relief. Also, insist that the doc check for metastasis to the stomach/digestive tract if he/she hasn't already done so. Ask for a referral to an internal medicine specialist if the oncologist can't help you. Best to get a 2nd opinion - find out what's really going on.
Sincerely,
Tre