I would go to the health food store and buy Sodium Ascorbate Powder (unless you have some) and take 4 TABLESPOONS today. Right now 2 and tonight another 2.
If they don't have any take the Ascorbate C powder.
Either one you can take in water or juice.
I would also take Echinacea maybe 4 tabs now 4 tonight. And I would suck on Zinc lozenges.
Also I would take Sambucol (Black Elderberry juice) 1 teaspoon every 3-4 hours.
And col liver oil at least twice the amount they recommend on the bottle.
I would continue to do that for the next week or two depending on how you feel.
Even if it is allergies or something else, it will not hurt you.
And if you do get the flu it will help your system to fight it off sooner.
BTW, cut out all sodas, sugar, diary, junk foods in general (unless you already do that).
Everything I recommended is alright for a bf mom.