okay so for two days now i have been in excruciating pain due to my tooth. I think its the tooth that i had a root canal done a couple of yrs before, and i need to know if its possible that it got infected again? or if the dentist didn't clean it out right the first time. the color of the tooth is changing and i could see it darkening even through the root canal white filling. All of my teeth on that side ( molars) are becoming really sensitive too. i have been taking loads of pain killers but the pain always comes back! Im dying here of pain so please can someone give me any advice. thanks