I created this account just to help everybody with this symptom. Sorry for my bad english.
First, i'm not a doctor, and this post is just for information.
I had a pressure in back of my head for 3 weeks. It started suddenly, and none painkiller worked, but finally i'm free.
In 3 days after it started, i was going crazy with that pressure and headache, i was afraid of brain tumour.
I visited an neurologist, he did a clinical exam (checked my eyes to see my intracranial pressure), my reflexes, pressure and blood circulation, all normal.
I asked it for a RMI or a CT Scan, then he told that based on clinical exam, that was not necessary.
He did a brain mapping on me, and found that my occipital nerves were causing the pain and the pressure. On the generated figure, the back of my head was incredible dark red.
He prescribed me clomipramine and escitalopram. I questioned him about these antidepressants. He told me it was not depression, these drugs can act on headaches prevention and muscle relaxation.
I asked about brain tumor, and he laught. He told that a brain tumor never causes a headache as primary symptom, even it does, it's not for so long. Usually, brain tumours causes loss of vision or body parts movements.
I questioned about the name of my problem, he simply told that a muscle pressioned an occipital nerve, it even doesn't have a "problem name".
About 2 weeks taking these medications, i am 90% better, and didn't had any side effect.
Don't worry about brain tumor guys, and do a brain mapping before any RMI or CT scan (that maybe exposes you to high levels of radiation and the risk of taking constrast).
If there is a tumour on your head, a brain mapping will figure out that something is wrong, then you should do a CT or an RMI.