Gator had a good answer for you, but I suggest you go see your dentist and let him check your teeth.
Why does my teeth feel sensitive and painful,fragile when eating ice cream i eat alot of gum usually spearmint or watermelon a pack a day. what's causing the teeth to hurt that way?
Your enamel might be wearing thing. Use Sensodyne toothpaste, and ACT restoring mouthwash. And quit chewing gum. It is really bad for your teeth, even the sugarless gum is bad.