Do you have any other symptoms, ie joint pains, sickness or anything else when the ulcers
erupt,? also do you get dry eyes or a dry mouth? when the ulcers are
Have you had the ulcers swabbed to see if they can pick what viral, fungal, or bacterial cause is.
It would be wise next time they come to have them swabbed,at your GP. to try find a cause as why they are recurrent, and keep coming back.