What to do if I am always getting canker sore in my mouth and tongue though I'm taking multivitamins. How can I cure this and prevent it next time?

Multivitamins. not all multivitamins are equal. you should see a "nutrition response testing" professional to determine exactly what you need. most vitamins in the store are synthetics and your body does not recognize them or use them. vitamins from whole food/plant sources work well. also think about breathing through your NOSE ONLY. you may be drying out the inside of your mouth if you breathe through it.