Hello and hope you are doing well.
Your symptoms could be due to a post nasal drip, which can cause a chronic irritation in the throat. This could be due to a sinus infection, a cold or a chronic allergy. It could be sinusitis, if it is accompanied by nasal stuffiness and facial pain or pressure. Post nasal drip could also be due to allergens. These are substances like pollen, dust, animal dander, certain foods, insect venoms and certain medications. Exposure to allergens causes a runny nose with a resultant post nasal drip where secretions from the nose go backward into the throat and irritate. You will need to consult your primary care physician for proper clinical assessment. In the meantime for relief from your symptoms you could do warm salt gargles and take OTC antihistamines.
Hope this helped and do keep us posted.
Good luck . hope these ideas help. Please keep us posted
The air conditioner is probably not helping much. You need to use a humidifier for nasal problems.
I suggest using a nasal rinse to help you rid yourself of the excess mucus.
Try drinking tea ( herbal is best ) before bed.
Eating within an hour of going to bed is not good for the digestive track...your body does not burn it off very fast while sleeping. Try eating at least 2 hours before going to bed. Rice should not affect mucus production.