Pain killers for sinus pain

I've been taking Panadol for 3+ months straight since my sinus infection started. I was taking 2 to 4 pills each day. But it seems to be not helping me that much any more. The pain gets pretty strong and it is really interfering with my work - it's a desk job but the pain is distracting and I find it difficult to concentrate on work. I went to a pharmacist who didn't really understand me and was not of much help, and I called up my ENT specialist who told me to stay on Panadol or have an early surgery, but there is not much else I can do.

I've tried some Ibuprofen, which helps much better, but the packet claims I should not take it for longer than 3 days! I need another month at least! I was thinking of taking some paracetamol + codeine, but I've heard some stories of addiction to codeine and damage to stomach lining even though there seem to be warnings about long term use on the box (!!!)

Does anyone know of a safe pain killer for my sinus pain that I can take for a period of about a month that I can get without a prescription? Or should I be looking for a doctor that is willing to subscribe me stronger pain killers?