Flu shot! At least for me, I starting getting them 5 years ago and never again got the flu. Yeah its too late you would have to wait until next year, but I know people who swear they would never get the shot, but I have to say 5 years and I have not gotten the flu. Before that I would catch the flu once every winter. This winter though, I didn't even catch a cold. Amazing for me. Also considering in NY it seems we would have one or two 60 degree days, then the next day would be 20 out. That fluxuation usually gets people sick. I also contribute it to being on Mega vitamins for a year now, and have been working out/exercising better then any other period in my life!
My advice, take vitamins not just C, rest, lots of food (force yourself) and plenty of fluid. Try to get out for a few minutes on the nicer days and walk a little. Even if its just up and down the driveway! Hope you feel better, I hate the flu!