I can also sleep off most headaches. When you find which points helps you, please let me know because I'm always looking to expand my knowledge of headache points and acupressure in general. The SI3 point is not one of the traditional headache points. I got suspicious about the SI meridian because I noticed that I was getting cold and numbness along its course prior to and during my severe headaches. Also, if a weather front was moving in, I got TMJ pain, and the meridian does run through the area for that pain.
Dehydration can definitely trigger headaches.
I have a niece that suffered from very severe migraines until she started drinking at least 8 glasses of water per day. Wind also can help to trigger a headache in her. Oh, that reminds me. She does relaxation exercises too, and she can't do beach scenes. The wind blows at the beach a lot.