I got a really bad toothache Sunday and was put on amoxicilin in preparation for a root canal today. By Monday night I was feeling systemically AWFUL- aching , nausea, fever, flu like symptoms. I realize some of it was the infection itself but my tooth got much better and with five days in on the rx I am wondering why I feel so bad. I am on the fentanyl patch for chronic pain but the aching is more than that relieves! Is this normal? The tooth was cleaned out today- necrotic infection and obviously the cause of the pain but I still feel lousy and like I have the flu. Has anyone else experienced this with amoxicillin?