Better you consult your dentist first

First of all check with ur dentist who has done the root canal treatment. Take a second opinion by taking X rays whether they are properly done or not. You have not mentioned whether the teeth are crowned or not and when did you undergo Rct and also are all the 4 teeth are paining. Secondly need to check the neighbouring teeth as well. Improper hygiene maintenance between the crown and the neighbouring teeth can also lead to decay of the natural teeth.

I'm sorry to hear you're in pain. You v have not mentioned which teeth you have pain in. Are v they b there the ones in which the root canals are done? Regarding sensitivity, I will recommend seeing your dentist to see if there is plaque or calculus deposition, gum inflammation or caries. I would recommend brushing twice a day to keep gums and teeth healthy.