Please tell me what can be the cause of chronic headaches?

Many sources: If you have yet to get a diagnosis, include a sleep test to determine if you have sleep apnea resulting in inadequate oxygen saturation

Headaches: A herniated disc in the neck can cause muscles to spasm and lead to tension migraines. There may be difficulty turning the neck, radiating shoulder or arm pain, and the headaches worsen as the day progresses. Imaging of the brain and cervical spine is a good starting point to eliminate the headaches. See a headache specialist too.