I brush for a little over 2 minutes, I count in cats and dogs (i.e: '1 cat and dog', etc...).
extended exposure to high concentrations of alcohol or hydrogen peroxide can strip skin off the inside of your mouth.
also might want to make sure your toothpaste isnt from china since they like to add ethylene glycol to it.
That actually happened to me...
When I used those crazy whitening toothpastes...
maybe you used too much???
Try counting in pigs and sheep instead.