I have exertional headaches all the time. Usually caused by laughing, talking a lot, strainig while having a b.m., or coughing. Mine don't last more than a minute or two. I also get migraines every month or two.
I know my exertional headaches are caused by a Chiari I malformation (enlarged cerebellar tonsils at the base of the brain, causing the brain to extend into the opening at the base of the skull). With Chiari, flow of cerebrospinal fluid is slowed or occasionally clogged by the brain pushing into the hole at the base of the skull. This intra-cranial pressure causes the headaches.
A cervical-spinal MRI (not a brain MRI) can detect if you have Chiari.
Hope this helps.
Doug