What Causes Hives,severe Joint Pain And Fever After Root Canal?

I've been in the ED 3 times this week. I had a root canal May 5th and have been having problems since. Hives, severe joint pain, loss of appetite, low grade fever, headaches. No one can figure whats wrong. My white blood cells count is 1300 and resting heart rate is 108 for the last couple weeks. I was told by my regular dr that it could be endocarditis. I had an echo done Friday which was clear and have had numerous blood cultures done. Any ideas of what this is it would be great.