Ugh, I hate canker sores. I hope it heals soon for you, alice.
When I was 12, I had a sudden… outbreak of canker sores. The entire inside of my mouth was covered with them. The insides of my lips, my gums, even a lot of my tongue were covered. It hurt even to swallow spit. 
I had to have a liquid diet through a straw, and even that was hard, because I had to have the straw pushed way back past most of the sores and near the back of my throat.
It lasted about a week. Ugh, that was horrible.