Sarah - figuring out if it's actually sinus or migraine is a good idea. I have chronic sinusitis, as well as migraines, and the sinus pressure can definitely trigger a migraine. Sinusitis is very hard to get rid of - but here are a few things I do:
Get a neti pot - this is actually used in yoga, it is great for clearing sinuses and keeping them healthy. It's a little pot with a spout which you put a mild saline solution in and gently rinse your sinuses - you can do it in the shower or over the sink. Used regularly it's great - you can find one on line.
Keep your environment humidified in the winter - sinuses need moisture and will hurt if it's too dry.
If I get an infection (green snot coming out) I use a nasal spray called AGcidal - it has a mild silver protein in it, which my doctor recommends for killing mild infections. If I get a really bad infection I go to him for antibiotics!
Dr. Robert Ivker wrote a couple of books called "Sinus Survival" which are really good.
Good luck! - Megan
Free My Brain from Migraine Pain www.meganoltmanfreemybrain.typepad.com