About a week ago, I had a sore throat and had a stre test done, but it was negative and I was diagnosed with a viral upper respiratory infection. The sore throat went away after a few days and then I had the typical cold symptoms (runny nose, cough, etc.). As of yesterday, the sore throat has returned and this time I have a white patch on the back of my throat. I had my tonsils taken out 18 years ago, so I would guess it can't be tonsillitis. Should I be concerned?