What Causes Swollen Throat And Tonsils After Recovering From Strep?

I had strep, been treated but, when I run out of antibiotics my throat swells and my tonsils become swollen with red veins on the left one. I have done blood tests for mono (negative), and strep came back negative. I have been taking Motrin, Benadryl, and Allegra D. I have really bad congestion.