You need to understand this better in order to make good decisions. Call your doctor tomorrow and ask him specifically what your diagnosis is. To have a finite one he would have had to do a biopsy. If you did not have a biopsy, he may be deciding that visually he thinks it is lichen planus, a tobacco related leukoplakia, or a herpes simplex infection. If something like that spread over your mouth that quickly, it may be a viral infection, not cancer.
HPV is human papilloma virus. If you chew tobacco you could have developed a large leukoplakia, which is not cancer but a pre-cancerous condition. You may be going to have this leukoplakia removed by laser surgery. ASK QUESTIONS NOW.