Pseudotumor Cerebri Support Group
Pseudotumor cerebri (PTC) is a neurological disorder that is characterized by increased intracranial pressure, in the absence of a tumor or other diseases affecting the brain or its lining. Diagnosis requires brain scans and lumbar puncture. Characteristic symptoms are headache, transient visual obscurations or transient visual loss in one or both eyes usually lasting...
http://www.ihrfoundation.org/intracranial/hypertension/info/C72/
Have you had a lumbar puncture to check your cerebral spinal fluid (csf) pressure? That's the one thing that can diagnose IH. Some doctors are reluctant to do it unless the other dandy criteria are met.
BTW... not everyone shows evidence of IIH in their MRI. Some do, some don't. I have an empty sella; not everyone does. Many people's optic nerves' changes can be seen on an MRI. My optic nerves are fine (no papilledema!) and there's not extra space around the nerves. My ventricles are narrowed but not drastically like found in some IIH patients, or not at all as found in others. Some people's venous sinuses look compressed on the MRI, other's don't. (Mine are small though I don't remember the exact words used - is that the same as compressed?) Anyway, certain signs might be seen but not everyone has those signs. A negative MRI finding isn't a reason to discount IIH as a possibility.
Sinus problems can cause intense headache, nose, ear, and eye pain. If it's in your upper sinus you may not even feel "stuffy." Just miserable. And if you are really clogged you may not even be blowing anything out your nose. Do you have allergies, or have you had that cold/flu that's been going around this year? All the strains are real bears.
There are lots of different types of headaches. Cluster headaches can feel like a knife through your eye. Check these out;
http://www.headaches.org/educational_modules/completeguide/cluster.html
http://en.wikipedia.org/wiki/Headache
There are neurologists who specialize in nothing but headaches. They are usually able to figure out what's going on rather quickly.
If it turns out you don't have IIH, be ever so GLAD. The main effects are a lifetime of pain, and possibly blindness. There is no explanation or cure. Just draconian drugs or surgeries that often don't work. It's a rare "orphan disease" with very little research. I bet you're thinking a diagnosis right now would be nice (and it would), but I'm praying for you that it's not this one.
In the meantime chin up. The doctors sometimes fumble around for awhile. Or a great while. But eventually they figure it out. If only we were all computers with source code to simply debug it'd be easier.