Mine was awful as well, it started around week 2 and didn't go away completely until around 6 weeks after treatment. All of my blisters around my gums merged together and pretty much formed one giant blister lining my gums... fun stuff. A dentist friend of mine gave me a very strong numbing gel that I would rub on my sores with a q-tip before I ate (or when the pain was unbearable). It would last about 20 minutes and seemed the only thing that would help alleviate my symptoms. Maybe ask your dental oncologist if there is anything he could give you?