How to tell wether or not ulcers in my mouth

Patient: How to tell wether or not ulcers in my mouth are canker sores or not. I smoked 1 cigarette on the weekend,which I never do and now I appear to have 4 quite bad ulcers under neath my young. But I’ve also been under a lot of stress I’ve ate badly and I’ve also been sleeping badly aswell. So I was wondering wether or not I might have been a canker sore. I can’t remember when I got the ulcer but it was within the past 4 days.

Symptoms: Sore ulcers when eating. Not painfull unless eating

Doctor: