Ulcers are caused mainly by stress ,indigestion or vitamin deficiency.Sometimes they could be viral in nature too .

There are multiple reasons for oral ulcers especially those which are recurrent and multiple. Multivitamins help to maintain the General Health of the skin but are not a cure to oral ulcers. Similarly mouth gels also provide temporary symptomatic relief till the time the natural course of healing gets completed. So you can continue to take multivitamins and at the same time avoid smoking and alcohol and spicy food that you have been doing till now. But the best recommendation for you at this time would be to consult a specialist like an oral pathologist or an oral medicine specialist for a proper evaluation of the case so that a rational diagnosis can be established. The right treatment can be instituted after the right diagnosis has been made. Regards.