Hi there. Causes for these headaches might be due to migraine, tension headaches, refraction errors, hypertension, missed hypoglycemia, stress, sleep disorders, cervical spondylosis, disc degeneration or prolapsed, could be the common possibilities. An intracranial space occupying lesion or an aneurysm need to be considered next. Get in touch with a neurologist for a detailed clinical evaluation and possible MRI spine and brain.
Hope this helps. Take care.
Well, since you feel it in your neck as well as your head, could be you wrenched your cervical spine somehow, or at least the muscles in your shoulders and neck. If it's your spine, you could have any number of things that happened, so a visit to a neurologist and a scan of your neck would clear that situation up.
But for the sake of easy solutions, let's assume it's your muscles in your shoulders and neck. The muscles go up from the neck and shoulders and up around the head. If they get strained or bunched up, it'll give you a bad headache. If you would have a friend or relative massage out your shoulders and back of your neck really good, several times a week, that will help. Also, apply heat to your shoulders whenever you can, either hot water bottle or lots of very warm tub baths.
Then there are postural things that can do this, especially as relates to working in front of a computer all day. While the eyes can give a headache, that's usually in the front. So, the way you sit would be the culprit. Me, I sit in a chair that has a high back so my shoulders sit fully back into the chair, I wear glasses that can see almost twice the length of my arm (an optometrist can do that distance, or ordinary dimestore magnifiers will usually have a pair or two that you can see more distance than the others), and I have a pillow I put in the small of my back. But work chairs don't allow for that sort of comfort, so you have to get up every hour or so, walk around a little, stare off into the distance, stretch, to keep those shoulders and especially the neck "tuned up."
Headaches, tho, can happen from eye strain, needing glasses, or sometimes a cavity in a tooth can cause a world of hurt in the head. Your sinus scan ruled out anything in there causing it, altho I have to wonder how come your nose was bleeding and running. If you happen to take antihistimines or other sinus medicines, stop taking them for a while, see if your headache subsides, occasionally those drugs dry out sinuses too much. You can use plain saline nose spray in the interim, to keep the clogs loosened up.
Hope some bit of this helps you find the source of your headache.