It sounds like there still maybe a residual infection present. I think the root canal might need to be retreated.
get an opinion from someone else---preferably an endodontist who has nothing to do with the practice you are in now. the tooth may have a fracture or residual chronic infection--more likely the former.
I'm going to the dentist who did it to get my teeth fitted for an appliance for sleep apnea. I will mention it then, if he is no help, then I will get a second opinion from someone else.
Something else that I forgot to mention is that when he did the root canal one of the files broke off. He couldn't get it out, so he told me about it and he left it in. (He didn't want to damage the tooth more by trying to get it out) He said it shouldn't affect the seal.... I completley forgot about that. I'll be sure to ask about that to the dentist and if need be, the person I get the second opinion from.
Do you think this could be part of the problem? I looked up files getting stuck in teeth, and it sounds like it does happen... and everyone makes mistakes, and he did what he could... I'm not the blaming type.