One of my fears.

When you don't know what is causing you to feel so bad, you can develop health anxiety. I know that I am constantly worried now that I'm going to have a bad pain in my head or neck.

Brain herniation is one of my biggest fears.

This is not my brain, it is a googled image.

Brain herniation, also known as cistern obliteration, is a deadly side effect of very high intracranial pressure that occurs when the brain shifts across structures within the skull. The brain can shift by such structures as the falx cerebri, the tentorium cerebelli, and even through the hole called the foramen magnum in the base of the skull (through which the spinal cord connects with the brain). Herniation can be caused by a number of factors that cause a mass effect and increase intracranial pressure (ICP): these include traumatic brain injury, stroke, or brain tumor.^[1]  Wikipedia.