Oh yes i feel your pain...back in April i had a root canal done, she started i could feel it so she gave me a shot of intrapulpal novicaine where they inject novicaine right in the root once they get the tooth open. This numbed it up and she was able to finish. A week later i went in to have it finished and when she drilled back in same thing i felt everything, so she gave me another shot of novicaine cleaned it out and filled it with an antibiotic. A week later i go back to have the root canal finished and again i felt everything so she gave me another shot, started again and i still felt it so she gave me another shot started and again still felt it, so she called out for the big kahoona and injected it again directly into the roots of the tooth, FINALLY that worked and she finished the root canal.
Unfortunately for me that tooth still caused me pain so i had to go to an Endodontist who found a hidden canal. The tooth is still causing me minimal pain but i've had two root canals on it and an apico on it with no success, so i know i need it pulled but refuse to pull it because i've got over three thousand dollars into this one stupid tooth, to pay 80 bucks to have it pulled would just aggrivate me even more!
When you go back if you feel it again ask them if they can give you a shot of intrapulpal novicaine it should work to numb the tooth so they can finish the root canal.
When they're giving the intrapulpal it will hurt like nothing before but only for a split second and you should be pain free.