Hello
Discolouration cannot occur in a wks time , you must have noticed now
Is it Ima single tooth , if yes then it can be because of some history of trauma
Generalised , then deposits in teeth
Next Steps
Visit dentist and get cleaning of teeth , if you want white shining teeth get bleaching of teeth
Health Tips
Brush twice daily
Try paste which are medicated and are used for whitening of teeth like shine n smile, Glodent or Glizer
Visit dentist twice a year and get cleaning of teeth