Sensitivity has a wide array of cause. You require a dental checkup to properly diagnose, followed by the treatment

Hi If your sensitivity is from a single tooth better consult a dentist For generalized mild sensitivity you can try senquel ad mouth wash and elsenz tooth paste , Proper brushing technq  is a must , check in YouTube for modified bass technq of brushing Better do a cleaning and polishing before starting the mouth was and paste. If you got night grinding of teeth may require a night guard

Hello Sir, Sensitive teeth can be because of multiple factors: seasonal variation, receeding gums, cavities, decayed teeth or worn out/fractured teeth. Please visit a nearby dentist to determine the precise cause and understand the treatment for the same.

Sensitivity may be due to any cervical lesion due to hard brushing or wearing off of the top most layer .there could be other reasons also .so go for the checkup .