Is it your teeth or your gums that hurt? If it's your gums, you may be allergic to something in the toothpaste.
Sensitivity to certain toothpaste ingredients is not unusual. It can cause gum soreness, or even gum tissue sloughing (peeling) like you peel after a sunburn. You should stop using it and see if the problem goes away. If you don't have sensitive teeth you don't need it anyway.
I like Prevident 5000 for tooth sensitivity and cavity prevention. Prevident is a prescription strength fluoride gel. It has more fluoride than over the counter toothpaste and not only improves sensitivity but makes teeth more resistant to cavities. You can purchase it from your dentist or ask for a prescription. One bottle lasts at least 6 months.