I Started Feeling Awful On Tuesday Night. Had Chills And

I started feeling awful on Tuesday night. Had chills and high fever. Next day same thing. I waited until Friday to see the doctor. He said it had the flu but should have come in sooner. At that point I had no fever but still had a slight cough. He prescribed hydrocodone cough syrup. 1 teaspoon every 4 hours as needed. I took 3 teaspoons with the 4 hours in between each dose. I feel worse. How long before this flushes out of my system? I should have left well enough alone. I wasn't feeling too bad when I had that doctor visit on Friday, but feel pretty bad now.