Hi there. This is Dr SATYA KIRAN, ENT Surgeon from Hyderabad. Painful sore throat as explained by u point towards a diagnosis of acute tonsillitis. Usually gets aggravated on consuming cold food items. The change of voice might be 'hot potato voice' seen in acute conditions.
Post nasal drip is an important feature of sinusitis, but in ur case there might be long standing adenoid infection & hypertrophy along with tonsillitis since childhood.
Next Steps
recommend ENT consultation
Health Tips
avoid cold food items, take steam inhalations, prefer to sleep side lying