Hi. Welcome to Healthcaremagic. I read your query. Oral ulcers can be a manifestation of several things like stress, anxiety,underlying diseases like gastric diseases, blood disorders, hormonal problems, medicine side effects, etc. Is your Hb level fine? any history of infection or medication? What is tha usual location of ulcer. Check if the size is small 1-2 mm, round margin, does not change shape.. these could be apthous ulcers. Take healthy diet incluting vitamin c, iron etc. Take multivitamin mineral tablet one per day. Tylenol or ibuprofen can be taken for pain relief. Apply anesthetic oral gel like Mucogel etc before eating anything to avoid burning. Maintain good oral hygiene. Avoid stress. Take proper rest and sleep. Check for indigestion or acidity and refer a physician. Take lots of fluids. If the antibiotics helped you, chances are there is some underlying infection. Refer a physician for Gastrointestinal check up. Hope the answer helps you. Thank you!