What causes migraine, how can i avoid it, what differenciates sinus headache from migraine?

Headache: There are many proposed theories on the causes of migraines from blood vessel constriction to cortical spreading depression. Some try avoiding triggers, but there is not good evidence for this. Sinus headache originates from sinus inflammation and swelling, not from within the brain as in migraine. Symptoms like nausea, vomiting, and visual changes or aura can help differentiate the two.

Headache diary: If you're trying to decide what sort of headache you're getting, the best all-around tip for headaches is a headache diary. This includes the timing and severity of your headaches, what you were doing prior to, etc. Also important is what you do for them and whether it works. Here's a helpful link to get you started. http://www.headaches.org/for_professionals/headache_diary.