Sinus infection or flu?

I had a cold last sunday, starting with the sore throat, post nasal drip, at first I thought it was my allergies again. Couple of days later it turns out to be a cold. With a slight cough, now i'm currently unemployed so I have no insurance to go visit my GP. I just bought over the counter stuff, decongestants etc. Okay well NOW exactly a week later, I feel TERRIBLE, body aches, when I cough up phlegm is green, but yet when I blow my nose it's clear.. is this allergic sinusitis, or do I have a sinus infection? How long will it last, I started taking an antibiotic