How can I get rid of a long term sinus infection?

I have had a sinus infection since I was diagnosed with swine flu september 28, 2009. I get terrible headaches and feel very fatigue. I also have been coughing and gagging up green mucus, sometimes brown with blood in it, or sometimes it white. I have seen 2 different doctors, one at school, and one at home. My school doctor said i had a sinus infection in november, by which I was put on an allergy pill. I saw him again in december, still had a sinus infection. This time I was put on penicillin and a decongestant. Over winter break I felt very tired and did not get out of bed for 6 days. My home care doctor tested me for mono, and strep. Tests came back negative. He put me on tamiflu and a val pack of steroids. Nothing worked, so when I came back to school, I saw my school doctor. He said he has no idea why my sinus infection wont go away, so he gave me amoxicillan 500 mg 3 times a day and mucinexD. I am on my last day of the 10 day treatment and nothing has changed. If anything I feel more tired, and more congested. How can I get better?