I quit smoking 6 months and 1 day ago and my canker sores are still a regular occurance. I used to get them all the time when I was little, along with everyone else in my family, so it may be a genetic thing, but in my 15 years of smoking I don't recall getting a single one. When I was researching them, one cause listed is "smoking cessation".
I have changed my toothpaste, tried different mouthwashes, drink lots of water, and I only vape tobacco flavors. I can relate to feeling depressed, they effect every aspect of my day to day life, can't eat (tiny bite chewed on one side of your mouth while moving your jaw and tongue as minimally as possible), have to drink everything through a straw, brushing your teeth hurts, talking hurts, smiling hurts, and it hurts to kiss my hubby and kids. None of them have ever had a canker sore so I don't think it is contagious/virus related. Surprisingly enough, vaping is one of the few things that doesn't irritate them!!
I have yet to find a pattern for when they occur, but they get worse for about 10 days of hell before they start to heal, and they usually come in groups. I have a nasty one about 2 days in on the inside of my lower lip, and I can feel a bump on the inside of my cheek and another on the inside of my gums where my tongue is, that will both most likely be huge sores within the next couple of days.
There are some great suggestions in this thread and I am making a shopping list of everything for next time I go into the city. It is nice to know that there are others out there who have had success treating theirs. Personally I feel like mine are getting worse/occuring more frequently and I am willing to try just about anything to be free from them (besides going back to cigarettes!!)