Given it's been 20 years I'm sure it's not anything obvious, but the main reason I get headaches is dehydration or blocked sinuses. Other likely reasons would

Given it's been 20 years I'm sure it's not anything obvious, but the main reason I get headaches is dehydration or blocked sinuses. Other likely reasons would be caffiene/sugar spikes. What is your general state of health and diet like, and stress levels?