I think mine are caused by a few different factors feeding off of each other. Eye strain, grinding my teeth, jaw pain, and stress. My doctor seems to think stress is the main cause. I chew on my lip when I'm anxious, which seems to trigger headaches. Then I grind my teeth at night because I have a headache. If I'm reading on my phone for too long, it seems to trigger a bad one. But almost all of my headaches start off as almost a mild neck pain, and then it slowly creeps through my head until I have a very intense pain behind my eyes.

I got my eyes checked. My vision is pretty much perfect, but I'm very slightly farsighted. My eyes correct for this so that I see fine, but my optometrist said that sometimes the compensation can cause some eye strain and headaches. I've noticed the glasses help, but I think they have the least impact. I use them when I'm reading or on electronics (they're also the kind that are supposed to filter out blue light, which might help).

I coughed up the $600 for a night guard (cries) and it's made a big difference. I also take a very small amount of a (prescribed) muscle relaxer before bed to help with any jaw/muscle tension that might trigger my clenching or a headache.

And the hardest one, I've tried to stop biting my cheek. This one is really hard since I typically do it without noticing. But with all these things combined, I probably get one headache every week or two instead of 4-5 a week, so I'm pretty happy.