Diagnosis? Bad Fever?

I have had a 103 fever for 4 days and it only goes down with Tylenol. I have no other symptoms whatsoever, except a slightly stuffy nose and I have a canker sore in the back of my throat, and when I eat I get a stomachache afterwards. What should I do? I'm desperate! I went to the doctors and they said I probably had a virus. Could it be mono? HELP ME!