After I stopped smoking, I experienced slight nausea and lots of fatigue the first week. So it's possible it's part of the withdraw process. But I don't know about the canker sores or the fever.
I quit 5 days ago, and I was definitely nauseous for the first 3. I felt like I was having hot flashes too, so maybe the fever is a result of that. I don't know if canker sores are connected at all, have you had them before? If outbreaks are stress induced, quitting may have caused that too.
Are you feeling any better?
Hows the not smoking and your symptoms doing?