Been experiencing symptoms since root canal

Hi,

5 weeks ago, I started root canal procedure with the dentist on an upper Molar. The next few days I was constantly lightheaded, awful taste in the mouth and when I bent down or did sudden turns, I felt dizzy for a few seconds and i had headaches everyday up to 3-4 hours at times.

I called the dentist and she said this could have been caused by bacteria in the mouth and removed a wisdom tooth on the opposite side and brought forward the appointment to finish the root canal procedure that Saturday as that was the only immediate appointment she could give. Also, immediately after the procedure I had to sign another form after spending 3 hours in the chair.

This root canal felt more difficult than another root canal procedure I had last year (bottom molar) and I felt a scalding pain near the end of the procedure. I told the dentist this. The dentist said that my roots for this tooth were long and twisty and went past the sinus line whereas the roots for the previous root canaled tooth were short and straight, very predictable she said.

I was hoping the completion of the root canal would resolve the problems but they have not. For the first two weeks after I still experience the short dizzy spells (seconds) with sudden movements, going up and down lifts etc and the bad taste in the mouth.
The dizzy spells with sudden movements are now rare and I don't experience headaches for as long anymore (did experience them for 3-4 hours) except when under pressure in work/trying to concentrate hard . My forehead feels like it is constantly under pressure and I am constantly congested and left ear very sensitive to noise

The dentist said that bacteria could have leaked from the root canaled tooth to the sinus line, but if it did, this is nothing to do with the root canal and it would have to have leaked by other means and that root canal procedures relate to the tooth area only and impossible for my symptoms to relate to root canal surgery.

Is it possible for complications to arise from root canal surgery?

Thanks,
Ken