Why headache occure?

Why headache occure?
Bioligacally, headache occurs because blood vessel in the pave the way are expanded and each heartbeat sends more blood pulsing through the brain and its covering membranes.
Personally, my headache occur due to stress, head trauma, or particular medication.
I know mine are bc of stress. I had this horrible headache on a sunday when my fiancee and adjectives of our friends went to bash in mexico. I be feeling sick and my guide hurt so bad I couldnt appropriate it anymore. He took me to the doctor and he said that it was bc of adjectives the stress I had at work and it headache usually show up during the weekend, when your mind and body are relaxing. It could also be something more severe, like cancer.
Stress ,coldness,and the illusion that we are traped contained by the body.