Sir, it maybe that your teeth are demineralised , or may be even eroded or abraded . In addition to all this there may be cavities
( small) which could render your teeth sensitive.Please consult your dentist
for erosions, abrasion of teeth and maybe cavities too.Eroded and abraded teeth can generally be restored with composite fillings
, and at times may require Laminates or veneers,in some cases they may have to be crowned or capped.Till then you can use Sensodyne tooth paste or Colgate Sensitive tooth paste.For relief from sensitivity.