According to Canary club, headaches in A.F. are caused by blood pooling in the abdomen and not getting to the head. Your scalp massages are increasing the circulation there.
If you do not have high blood pressure, Veg, try a variant of the yoga posture The Reverse posture.
A photo and description of it is included on this page (you will have to scroll down): http://www.yogapositions.net/yogapositions12.php
Do not stay in it for more than a minute at a time, though you can do it several times a day. In the future, you will be able to increase your time in this posture.