dear friend ,
thanx for sharing your concern,
A successfully treated root canal
will have no pain, even after two to three weeks of treatment .
it seems in your case some canal has been left unexplored and untreated which is causing you this pain .
you can visit your dentist
and get an xray done for the RCT treated tooth .
i would suggest , to go for a second opinion
too. in this case you don't have to bear this pain.
after getting root canal done.
it is curable .
get an IOPA done and proceed further .
mean while, take painkiller for two to three days, combiflam
hope this helps,