Things that come and go are not cancer.... it doesn't go. 99.9% of people develop some kind of abnormality in their mouth about once a month. Of course they are mostly not serious and resolve on their own with or without treatment in a couple of weeks. If this thing is still around in 2-3 weeks, time to go to the dentist to have it checked out. 5 years is way too long. You can find a dentist that is sympathetic to this phobia, which is actually quite common, and write you a Rx for something to calm you down before your appointments. But if you persist in not seeing someone when something goes south, you won't know early enough to fix it- whether it is a simple decay and filling, or something really serious.