Hi..... Sounds unbearable. I've had a lifetime of headaches. Found lots of possible reasons. Never answers from any doctor. Had much improvement when I got an infected root canal pulled. Which was an incomplete root canal done over 25 years earlier. No doctor ever noticed. Luckily, a specialist noticed when he was doing root canal on tooth next to it . Also had much improvement of severe cough from constant sinus drainage at same time. Seems docs also ignore sphenoid sinuses which can cause severe headaches. Docs seem to only know about pain from frontal sinuses. Did you happen to get a covid vaccine or booster just before your headaches started. Seems to be another possibility docs are sworn to ignore. Allergies or ( sensitivity) to some foods got worse after my vaccines . Setting off new headaches. Such as nuts, dairy, processed meats. Did you get tested for parasites? A simple infection is also ignored by docs if you don't have usual symptoms in blood tests or no fever. Antibiotics always cleared my sinus drainage, without usual infection symptoms. Docs always refuse to give antibiotics for months, claiming it's always viral. But for over 25 years, was the only thing that fixed my cough, headaches,drainage. Constantly not noticing the constant infected root canal.
I believe you'll find some answers. Keep a diary. But don't expect any doctor to believe you, even if you have the exact same thing happen , year after year. Because they don't believe infections exist without a fever.
Good luck. Praying for you. Keep looking. T