It would be best to see a doctor for advise & consultation.
What you experienced is probably only the common COV flu & not the evolved strains of COVid 19 that PCR & ART was designed to detect. The cause of your flu could be due to over-straining of your immune system - either pushing too hard at work or exercising, over stressed, lack of proper food/nutrition, not enough sleep, & coupled with the change in seasons - hot & cold with sudden rains, making the body having a hard time to adapt, & the flu virus won.
Usually, within just a few days of rest & a proper diet, one recovers. To help:-
1)Keep your chest area covered & warmed, button up to the last button, as that's where the virus is building up, & would be conducive to its survival at temp below 36C. Also, never allow fan or air con to blow directly into that chest area, as it needs to be warm to help the immune system to destroy the virus.
2)You will feel fatigued, or with mild headaches. Take special panadol - Cold Relief, as it comes with caffeine & help eliminate lethargy. 2 pills a day will do the job,
3)Use Salonpas spray to spray outside the throat/neck area. It will help relieve the pain when coughing or have trouble sleeping at night.
4) Use a nasal anti decongestant spray if a running nose develop
5)Keep your body warm where possible - under the sun, with thicker clothings, or blankets, as the immune system will need the help of heat to destroy the virus which will not be able to survive above 35C inside the body.
Good luck, all the best & wish you a speedy recovery. :-)