For the past month I've been having throat pain on and off. It's been hurting to swallow and breathe. Sometimes it's in the morning and at nights. Sometimes it's on the left or right or both sides. Now it's on the right side. Been to the ER twice. My test for mono and tonisilitis and strep were negative. Although the ER said my tonsil and uvula were really red and sort of swollen. What could this be?