I don't have any specific suggestions for you about headache causes.

Curetogether is crowdsourcing site to help people help each other figure out what's causing their health problems. The founder started it to deal with her headaches: http://quantifiedself.com/self-experiment/ http://curetogether.com/chronic-daily-headache/survey/symptoms/

Time of day seemed to be a significant factor in discovering the cause for her. That may be something you want to add to your logs.

There are always a lot of factors, and formalizing your experiments may help you figure out what the most significant causes are. You may want to try eating the same things every day for a while, at the same time, to reduce variation. You may also want to do things you don't usually, and stop doing things you do every day.

Chronic pain is a huge drain on one's life. I wish you all the best in moving towards decreased pain.