It's called let down migraine. I get them too, mostly at night when I'm done with doing things for the day. Sometimes I make more projects for myself so that I can put off the pain for a bit longer.
https://migraine.com/living-migraine/navigating...
Here is a pretty good article about it. Most things about the brain are a mystery, but if your pain happens like clock work you can plan for it. What is your pain like when it happens?

Hi, no luck. Thanks!!