Help! I'm losing my singing voice! Now what?

Hi. Around the evening of Thanksgiving, I became ill with alternating chills and high fevers (up to 100.8 F). This has since turned into high post-nasal drip and a painful sore throat, and my mucus has been either yellow-green or a thick red-brown. I consider myself a skilled tenor, and I do not smoke, but I am very worried that I am losing my singing voice because there is so much phlegm in my throat. My speaking voice has also become low, gravelly and raspy as a result of this. Can I get any advice (preferably from fellow singers) on how to clear this up--what OTC or prescription meds I should be taking, etc.? I'd really appreciate it.