Severe Sore Throat, Does Not React to Z-Pack

I've had a severe sore throat for about a week. My doctor prescribed me a Z-pack of pills, and it's made a little improvement. No fever, no cough, no body aches, not NOTHING! My throat is just red and it looks like I have red bumps all over the back of my throat. I developed a canker sore under my tongue (I don't know if that's incidental, I have been test for HSV and I'm negative). I don't know what this could be?! This same sore throat came on about a month ago, and was gone on it's own after a week or so, now it's back again? could this denote something more serious? Should I further inquire with my doctor?