Hi. Thanks for your query. Noted the history an understood the concerns. Diverticulitis is a recurrent problem and it does not guarantee the response to treatment every time you have an attack. Development of the Canker sore indicates that your immunity has been reduced so much and may be the another reason for delayed response to even 14 days of antibiotic cover. It also indicates that you may need a changeover to another antibiotic and addition of Vitamin A and D in therapeutic dosages, multivitamins and probiotics. Add on Diverticulitis diet under a Dietitian s directive. Get on the examination of blood, tests and urine along with CT scan of the abdomen to decide the current position of the disease and any other complication. Get a clinical evaluation and examination by a Gastro Surgeon to know the proper diagnosis and future course of management.