Yes the tooth needs root canal treatment, get the treatment done as soon as possible please ask the doctor to adjust the dental chair which you are sitting in such a way that u will not have gag reflux. (Probably a straight position of patient back will allow to have less gag)Ask him to give short breaks during treatments and most importantly dont try to breath with your mouth and dont try to swallow water which comes out of drilling unit(airotor)
Next Steps
get root canal treatment as early as possible
Health Tips
cooperate with the doctor and follow the above mentioned suggestions.