Dan, as I previously advised you need to see an ENT or oral surgeon. Not all dentists check for oral cancer let alone diagnose it. Unfortunately many are not up with current medical findings that oral cancer can be found in younger seemingly health patients. Brushing the heck out of it is like ripping off a scab, it makes it appear that the sore is gone but its really still there underneath that top layer. Please avoid shooting that spot with a waterpik. I know you are anxious and want to know whats going on but it takes time. Even if you see a qualified ENT or oral surgeon tomorrow and they do a biopsy it will take another week for the results to come back.
How about attending the OCF's Philadelphia OC Awareness Walk on Saturday? Its at a dental school and they will have specialists on hand doing oral cancer screenings. They may be able to fast track any unusual findings to a qualified professional. Hurry, registration closes 4/5/13 at noon. You can still attend if you miss the deadline but may not get a tshirt and registration will be $30 instead of $25.
OCF Awareness Events (OC screenings at events)