I regularly get mouth ulcers and already have aroind three of them. what could be the reason? syphilis? cancer or just normal ulcers? scared!

Aphthous ulcers: The painful white ones in the mouth rather than on the lips are usually harmless. I trust you do not have lupus, Behcet's, or a low neutrophil count and are otherwise well. These are not cancer and are not syphilis.

Canker sores: The most common mouth ulcers inside your mouth are canker sores. They can be quite painful but usually heal within 2 weeks. The chance of cancer at your age in minimal. See a dentist to find out exactly what is cause ping these ulcer. Canker sores can be related to trauma, stress, sensitivity to certain foods or additives in toothpaste, vitamin deficiencies, autoimmune problems and other things.

See below: The most obvious would be apthous ulcers, which can be caused by stress. Have your dentist do a clinical examination and if this is the case, laser therapy may be able to lessen the duration. If you feel this is not the case, contact your MD for a complete workup.