There are many different issues that can be going on in your mouth. A doctor can only give an educated guess without doing a biopsy. Trying to treat their "guess" isnt the best way to go about this.

First... if you have not yet quit smoking do so immediately. There are many known cancer causing ingredients in all forms of tobacco so you never know what could be causing irritation. Eliminate tobacco for good!

I recommend seeking out an ENT who specializes in oral cancer. They are most likely to have the necessary experience to properly diagnose you. The rule goes like this... If you have an unknown sore or irritation in your mouth for more than 2 or 3 weeks and it does not resolve itself then seek out an experienced professional (ENT). Honestly, I would not put myself in the hands of a doctor who was playing guessing games with a diagnosis, find an ENT who's specialty is oral cancer. Im NOT saying thats what I think it is, its not possible to diagnose someone over the computer. What I do know is a qualified ENT would be the best source for you to get diagnosed with whatever you have going on.

Its likely to be a few weeks before you get an exact diagnosis. Plus by seeing an oral surgeon, they most likely will advise surgery just like any specialist will advise their own line of treatment. Thrush is nothing serious and usually is a thick white coating in your mouth not like what you described.

Hope its nothing serious! Best wishes!!!