Have you been seen by a doctor? The pressure can be caused by two things.

The most concerning is the mechanism in your brain that controls blood pressure is not working properly. This is what happens when Second Impact Syndrome comes into play. The over-pressure can cause serious damage.

The second is caused by neck injury with related muscles spams and inflammation of the joints in the neck. This can disrupt blood flow and cause severe head aches, too.

Either one should be looked at by a specialist in concussion and upper neck injuries. Good luck finding a good one. They are hard to find. Most doctors do not have this level of expertise.

Do you have a blood pressure measuring kit? It will help if you check your pulse and blood pressure when you are experiencing these extremes.

Do you consume any caffeine? It can be counter to the head ache issue. You should limit your caffeine to one serving per day, max.

Keep in mind that a concussion is not a one time event. It is a cascade of events started by the impact/injury. That cascade can take 6 weeks or more to stabilize. I have had up to 3 months of increasing symptoms. 3 months is not uncommon but 6 weeks is a more common time frame.

During the cascade, the brain is much more susceptible to dangerous injury. Each consecutive impact causes an injury that can be a level of magnitude (multiplication of the previous injury not adding to the previous injury) more damaging.

Hope this helps you understand the mechanism of concussion.