I am a sinus headache sufferer myself. I have found great relief in a simple remdy - sterile saline spray - do it faithfully everyday, makes a huge difference. If your sinusess have been acting up for some time- its probably an allergy. Do you have a humidifier at home/work, makes a huge difference, drink lots of water.
If you have a sinus infection you really need to get to your doctor for some antibiotics to knock it out of your system.