Pain underneath bridges/crown

I had a dental procedure to fit in briges (6 Emax crowns)  on both sides of my lower jaw  (back teeth) six weeks ago. I have felt pain in the fitted area since then, but now only in the molars holding the bridge on both sides of the jaw.  The pain feels like its coming from the root of the molars and is relieved by Ibuprofen. I can not chew even vegetables without pain. I have been on a soft diet since the procedure. The dentist prescribed antibiotics for 5 days and painkillers and suggested a mouth guard at night! Even after 6 weeks is still advising to continue with painkillers and to "relax". Because I had the procedure done abroad I decided to consult another dentist locally. An xray done showed no infection or abnomailities. Meanwhile I am still in pain and painkillers have become my lifeline. The same sore teeth are also very sensitive to heat and cold. I had laser teeth whitening before the procedure. I am wonering what to do and what could have gone wrong.