I am a 20 y/o f, sinuses full- over-the-counter meds haven't worked, coughing up green/brown phlegm for 3 days now.

No antibiotics 4 URI: We used to claim that we could differentiate viral upper respiratory infections from bacterial ones based upon the color of phlegm or nasal discharge. Greenish brown icky stuff was supposedly of bacterial origin & deserving of antibiotics. However, we now know that not to be true. Most uris are viral in nature & won't respond to antibiotics. Worse average cough illness lasts 18 days so be patient!

Infection: Sinus congestion can occur with allergies and colds. Sinuses can become infected acutely with symptoms of pain, nasal stuffiness, cough, congestion, fever and bad breath. Chronic infection has symptoms of facial fullness, nasal blockage, fever, and discolored phlegm, and fatigue. I would consult physician for physical exam, possibly imaging and for proper therapy.

Check with your doc: Sounds like you need a lot of intranasal steroids to get your sinuses cleaned out. Ocean spray can also help.