I don't get the flu often...or colds. But I had a mild virus two or 3 years ago, and I had full body burning with it, for 3 days.

I took AlkaSeltzer for it, and that helped. (this blocks histamine receptors).

Then a year ago last Feb, I had a severe cough thing. No fever, just an endless cough. I took guaifenesin with DM for almost 2 weeks, (about 80mg of DM /24hrs) and my feet STOPPED hurting throughout the whole thing. So now I take some only at bedtime, and it seems to help that one hr trying to fall asleep.
I had a post about it back then even.

Dextromethorphan is a NMDA antagonist, and it has been tried for post-surgical pain with mixed success. Nide here tried it at his doctor's and it did not help him. DM is not really going to work for everyone, but I was interested that it worked for me some. The mixture seems to help with sinus drainage for me too.
One cannot use it if on SSRI drugs or other antidepressants.

What medications did you take for this flu if any? Might be a hint there.

Ladders are definitely not good for people with foot issues. Mega painful stress on the bottom of the feet!!