Recurrent oral ulcers can be due to multiple reasons. You can at least eliminate the causes which you have been able to identify like spicy foods. For temporary symptomatic relief you can use anaesthetic ointments like dologel CT or any ointment containing benzocaine or lignocaine. If your blood sugar is not within limits then healing of any wound would be slower and the ulcers will Heal in a longer time as compared to any other person. Please do not hold this misconception that you cannot take a healthy diet because you are diabetic. Consult your diabetologist for a proper diet chart in which you can get all the nutrients without the components which can increase your blood sugar levels. Gastric problems like acidity can also be one of the reasons for oral ulcers. Having a regular diet schedule and healthy diet rich in fibres can be fruitful for this case. You can consult your physician regarding any other aspect of your gastric problem. And most importantly a proper clinical examination by a dentist will be the most prudent step for a rational diagnosis of your problem. Regards.