Nausea, loose stools, fainting on walking can be due to gastroenteritis
Congested nose can indicate towards viral cause as a possibility.
Feeling hot in spite of air conditioning indicates infection has spread into blood also.
Hence I would advise you the following:
Consult your Doctor for examination and clinical evaluation.
Get the stool and blood tested.
If there is bacterial infection then you need a course of an antibiotic, probiotics and Metronidazole
Fluid and electrolyte replacement if there is no vomiting
to control nausea.
Use only boiled for 20 minutes and cooled water.
Continue the pills unless told otherwise by your Doctor.
Hope I have answered your query. Let me know if I can assist you further.
Dr. T Chandrakant,