We do not deal with these types of problems. Your best approach is with an ENT and possibly a neurologist, both of which you have seen before. This has nothing to do with allergy.
Please post your question with the Neurology Forum at http://www.MedHelp.org. The neurologists at the Cleveland Clinic answer these questions. They have more experience with chronic headaches.
Sorry to comment on my own post but I was cutoff by the word limit.
I believe these type of headaches (barotrauma) are extremely common and virtually unrecognized by most doctors (at least that I've been to). My wife, mother, and mother inlaw frequently have headaches (not as severe as mine) in their face on the same days as mine. We call them bad head days.
The ear nose and throat Dr.s I've been to seem obsessed with congestion(mucus) and controlling it, believibg it to be the main cause of pressure. If you read military medical literature on pilots with barotrauma you learn that mucus is a godsend. It eventually stops the headache.
When a vaccuum headache (low pressure in the sinus) develops due to rising pressure in the environment and a sinus sytem not able to equalize it, the vacuum pulls the passageways (sinus windows/septum etc.) shut, just like a door can slam when the wind blows, effectively sealing in the vaccuum and causing pain/discomfort. A buildup of mucus behind this pulled/sealed area eventually relieves the vacuum due to the weight/volume of the mucus and as the "pull" relieves the passageways open and the mucus drains out.
This is probably why everytime I take a decongestant my headaches get much, much worse.
I wish I could find a ENT that takes barotrauma seriously without joining the Navy and becoming a pilot. These headaches greatly affect my life.
I have a 21 year old son with asthma but since having an air purifier in my home that covers the whole house; I've found it to help all my children even in the midst of this WI winter - we've had no colds or flu or other respiratory ills. Here's some obvious signs in your own home that can indicate a need simply for whole house air purification.
COMMON TRAITS OF INDOOR AIR POLLUTION
Affected Household Members initials: ____ ____ ____ ____ ____
Dust on furniture / Visible in air
House odors
Allergies
Asthma
Sinus problems
HEADACHES.............................
Sleeplessness / Light sleeper
Snoring
Sore throats / Colds / Flu
Itchy/ Watery eyes
Coughing / Throat clearing
Lack of Concentration
Depression / Irritability
Fatigue / Naps
Mold / Mildew in basement & bathrooms
Pet dander and odors
Smoking
Wood / Coal heater
Static Electricity
As you fill this in and realize how much is affected by your indoor air; maybe you should try an ionizing/ozone air purifier like I have. It's removed all respiratory ills in our family with 8 children 19 down to two. I know breathing in that purified air night after night in and out, in and out has healed our lungs and even strengthened our immunes systems. My air purifier is no medical machine, but it's sure amazing how good you can feel breathing in purified air that's cleaned like fresh air outdoors.