For some reason, my mom's mouth recently became so sensitive that it was hard for her to eat anything. When she tried gargling with sesame oil, it helped her mouth feel better--even though she says it tastes awful.
I also had sensitive gums a few years ago--I think I was brushing too hard. Anything hot, cold or acid (like vinegar or lemon juice) really made them hurt. Avoiding these things helped, and so did brushing more gently with Sensodyne toothpaste. (I hadn't yet read about the benefits of sesame oil.)
Possibly, taking more zinc eating more fat has helped also. These are both good for your skin; they may be good for your gums also. And now that I no longer eat a starchy, sugary diet, I don't feel any need to brush hard, just normally and gently.
If your mouth hurts, try avoiding cinnamon, too: it's an irritant. Remember the bee-stung lips fad from a few years ago? Some of those plumpers used cinnamon as an active ingredient. For those who use cinnamon to slow gastric emptying, it's available in capsule form.
If it hurts to chew anything, let me share my protein shake recipe with you. This is what I have every morning; the supplements are optional.
1-1/2 cups water
1 heaping tablespoon rice protein powder (chocolate)
1 heaping tablespoon nut butter (without sugar or cinnamon)
1 tablespoon olive oil (optional)
2 GNC Hair, Skin & Nails Formula vitamins (optional)
250 mg magnesium (optional)
100 mg zinc (optional)
18 mg iron (optional)
1/2 teaspoon xanthan gum (required)
Put everything but the xanthan gum in a blender and blend until smooth. Add xanthan gum (or some other thickener) and blend again.