I should add that I was never diagnosed with the flu, although I was not well for several weeks. I am mainly trying to learn why harsh esophageal reflux seemed to occur so suddenly, when I have always been able to eat all the "wrong" foods, before.

Hi
Welcome to healthcare magic forum
Oesophageal reflux can be due to many causes like over eating, anxiety, stress, sleeping /lying down right after a meal, obesity, hiatus hernia etc. Try to idenify the cause if possible. Swineflu or any flu for that matter is unrelated to this.Use to pain killer medicines can worsen these symptoms..so if you are taking any plese stop.
Try to take small, light meals. Avoid heavy & full meals at night. Avoid lying down after food ..for atleast 2 hours. Milk helps a lot. Stress, anxiety and loss of sleep causes and worsens acidity & reflux.
You may try homoeopathy as well.
takecare

Thanks for answering.

I'm not using painkillers, obese, or able to eat heavy meals.

I have done heavy lifting but did not seem to strain myself.

I have been under much stress.

Welcome to HealthcareMagic Forum
Stress is one good trigger and maintaining cause of acid reflux and similar illness. So be nice to your body and mind.
Takecare.