I have had severe pain beginning with my right side radiating under breast.hurts to breathe or lift arm. ulcers in mouth and in corner of mouth, sores?

Skin ulcers:shingles: Severe pain from your backbone to your mid chest on one side, along with mouth ulcers and sores can describe "shingles" a type of herpes (zoster). See your healthcare provider for tests and antiviral therapy.

Chest pain: The mouth ulcers and the chest pain may be related. Viral process associated with a pleurisy. However the new onset of chest pain associated with pain to your breast and hurting to breath warrants getting checked.