How can I tell if I have a migraine or a sinus headache?

CT of head/sinuses. A good clinical exam can usually distinguish a migraine from sinusitis. The definitive exam for sinusitis is a ct of the sinuses. A ct of the head is important for migraine.... But usually a good exam by a neurologist can determine if you have migraines.
Nature of pain. Migraine headaches can often be triggered by exercise, red wines, certain foods, stress and sleep disorders; the pain is usually on one side of the head and typically throbbing. Sinus headaches are often bilateral and tend to be on front of the head/face; pain is often pressure like. Consult your pcp for a comprehensive evaluation.