There are a number of possible causes.

The location of the head pain may point to the reason. Can you tell us where your head is hurting specifically when you get one?

Here are some possible culprits:

Pain in the ears and side of the head - can be from unconscious hard Teeth Clenching from stress plus minor jaw misalignment. A doc prescribed muscle relaxer will stop this.

Pain at the temples - often accompanied by slow-moving bowels. Usually from a change in diet, dehydration, travel or a disruption to one's normal daily schedule. Taking a couple of magnesium tablets at night before bed for a few days should relieve the problem. ( I take two every night)

Pain in the back of the head or neck - Could be from poor sleep positioning and a neck out of place. The neck vertebrae is very easily put out of alignment by improper sleeping positions. Buy a wedge pillow and sleep flat on your back (no side or face sleeping!) for at least a month to realign your spine and allow any inflammation to subside. Also, a chiropractor may assist in resetting anything gone awry.

All over head pain - may be a food allergy. Several of my family members developed severe head pain after going to a particular restaurant and eating Mexican food. It was always triggered after eating there and eating this food. Food prepped at home did not do this. It had to be an ingredient used in the restaurants.

Caffeine withdrawal or overuse - if you usually have daily caffeine and then go without for a day, the small capillaries in the head will engorge from the rebound effect. Take some Excedrin which will fix this up. Excedrin is a 3-drug combo: Tylenol, Aspirin + Caffeine. It is my go to.

Also - Too much caffeine combined with a neck that is out of place will cause severe neck and head pain. Got to the chiropractor and drink lots of fluid and Vitamin C to flush the excess caffeine.

Think about what precedes the headache to get to the bottom of it. Good luck!