Can be due to,
1. Cavities in tooth, can initially manifest as sensitivity(Deep for dentinal)
2. Chronic food lodgement followed by improper brushing of teeth leads to further accumulation of microorganisms, which forms calculus. Sometimes it results in sensitivity.
3. Chronic acidity, it leads to wearing off of enamel layer. Which further leads to sensitivity of teeth on hot or cold intake.
In your case it's most probably presence of cavity in some tooth.
For the time being,
T.zerodol P, half a tab after food, if doesn't relieve completely,have the other half of tablet.
T.Rantac 300, once a day before food.
Next Steps
visit dentist and get evaluation done thoroughly
Health Tips
avoid very hot/cold/hard/sweet/sticky food
soft diet
do not neglect brushing after meal.
hold mouthful of Luke warm salt water in for sometime; you can do it for few times a day, if it's relieving your symptom, even partially.