Hello mam...
Sensitive teeth sometimes called as Dentin hypersensitivity is due to Overzealous tooth brushing,A stiff bristed brush or over abrasive tooth paste...
some times acid reflux , bulimia also causes erosion of enamel and causes tooth sensitivity...
it may be due to imperfect bite, Grinding or clenching teeth, Gum recession, tooth decay, cracked teeth...
first and foremost x-ray has to be taken to check for tooth decay....
complete clinical and radiological examination is necessary to rule out the cause...
treatment option also vary based on the diagnosis... in case of cavity you need to fill the cavity...
Next Steps
kindly visit dentist for furthur clinical examination and management