If you are young, this is not common at all.

Low profusion of blood to the brain, sounds pretty serious to me.

There are autoimmune conditions like lupus, and others which
inflame the interior of arteries, and cause blockage of them and hence poor circulation.

Also a condition called Marfan's syndrome which is inherited can affect the walls of the blood vessels. This usually starts with the aorta, which can balloon out, and finally dissect and rupture to a terminal end of the patient.

Here is a rather complex explanation of low blood perfusion, I found today:
http://en.wikipedia.org/wiki/Intracranial_pressure

I think your question is beyond the capabilities for simple intervention on the net. I think you need to see a good doctor who can explain this to you and find the cause of yours.

This is the keyword I used to find this article:
"causes of low blood perfusion to the brain"

There are other articles that come up on Google with this search, and all of them are medically complex.