I have had this problem on and off for 15 years and it's a royal pain. My dentist and family physician have each prescribed "Miracle Rinse". It's an Rx that is made up by the pharmacist. Several ingredients can be used but mostly it's lidocaine, mylanta (used as a base), benadryl and sometimes nystatin if they think the sores are caused by yeast. You simple rinse, swish and spit. Can be swallowed as well with no problems. Also, I use Peridex mouth rinse and Biotene toothpaste . It does not have SLS in it that can really irritate a sore mouth.

Good luck and hope you are feeling better soon. I just got over a bout of ulcers. They even make it difficult to talk properly!