I Had Root Canal One Years Ago With The General

I had root canal one years ago with the general dentist. but after root canal, my teeth was still very painful. So I request to have second time root canal because I througt the root canal was failed. after second time of root canal, I feel infection getting better after take 3 bottle of infection or inflammation medication, but I still have bad taste and smell in my mouth. I'd like to know it is root canal problem or gum problem. Until now I still have same problem. I really need your help because I have visited endodontics and periodontics. They all told me my root canal and gum no problem.