The best chance of you becoming headache free is to tackle your headache in several different ways at once - a multidisciplinary approach. THis includes evaluating for neck problems which contirbute to headache and dizziness, headache psychologist, physical therapy to the neck, biofeedback, and medications.
Good luck
Several weeks ago I experienced very similar symptoms you had: chronic headache, massive ear ache, ear fullness, dizziness, nauseousness, and vertigo that lasted two days and suddenly went away. I also ended up getting paralysis on the right side of my face (later diagnosed with Bell's Palsey). Eventually, after MRI, Spinal Tap, x-ray, and blood tests, I was diagnosed with viral meningitis, resulting in nerve damages to my ear and a mild case of Bell's Palsey. They put me on Prednisone for the nerve damage to my ear. Unfortunately, I'm having a lot of serious side effects from the prednisone...i'm feeling worse than before. While this may not be your condition whatsoever, as i'm only a patient, maybe you can discuss it with your doctor re vestibular labyrinthitis: http://www.betterhealth.vic.gov.au/BHCV2/bhcArticles.nsf/pages/Labyrinthitis_and_vestibular_neuritis?OpenDocument. GOOD LUCK and I completely sympathize.
One more comment: I too was on several types of antibiotics, including amoxicillin, augmentin, cipro, and levaquin because they thought it was a simple ear infection. After being on 4 strong types of antibiotics with no relief and worsening in my condition, that's when they did a spinal tap and found it was meningitis.
Chronic pain, so that you don't risk any loss of credibility with your doctors because of my stupidity, please allow me to modify my comment.
Holding your nose and blowing into your ears would increase pressure in your middle ear, not your inner ear. Also, the anatomy of the inner ear appears to be such that the pressure in your inner ear will be the same as in your CSF.
The periodic episodes of vertigo and feelings of fullness in your ears you describe are both symptoms of Meniere's disease.
I do still think it might be a good idea to assess your CSF pressure.
This is pure speculation.
When you blow into your ears by holding your nose, you increase the pressure in your inner ear. If the pressure in your cerebrospinal fluid (CSF) is so high it is pressing your brain, which is soft tissue, into the openings of your skull, the momentary increase in the pressure in your inner ear could partially balance the too high pressure in your CSF, giving you a brief feeling of relief.
Ask your doctors to measure the pressure in your CSF.