Many thanks to all of you (Mark, Bud, and Microman). Your advice makes perfect sense and I will follow it.

I am starting to think that my neck might be involved in the y headaches, since I realized that cognitive effort while lying in a good position is not aggravating the symptoms, so perhaps it is only the seated or standing position that triggers the headaches. I will report on any progress here in case it can help others.

Matt, I wish you all the best in your recovery.