Crown placing

1 month back i have gone through crown placing for top left teeth second one from back. before placing the permanent crown, initially they had put some temporary crown and that time i didn't get any kind of sensitivity. After fixing the permanent crown i am getting sensitivity problem for cold water. If i touch that crown with my finger, it is smelling badly and paining also. 5 times adjustments were also happened but still the sensitivity is there. i use to get some kind of itching feeling around the crown and inside the crown i am getting feeling like something is pulling. i am not getting severe pain but i am getting pain.dentist has suggested me to use SENQUEL-AD mouth wash (rinse  daily two times morning and night after breakfast and dinner). i am using now, there is some betterment. she suggested me to use for one month. she is telling that, if there is sensitivity even after one month, we will do root canal and fix the same crown. what is root canal? will it be painful? why i am getting slight pain. doctor is telling that the pain will go off in a month... please advise on what to do further.