Dear vd007,
I am sorry to hear about your condition.
Let me try and find a few perspectives to see this matter from.
About the sensations going on in the head and on top of the head: A picture/idea that I like is that the energy in the body and around the body is such: The energy flows up along the spine, out of the head up and to the sides (like a fountain), and comes in again through the feet. (The idea is, that one is standing.) One could make a movement with the arms to encourage this feeling of spreading above the head, dropping along the sides, and allowing to come in to the feet again. If this is new to you, do not do it more than three minutes.
About doing slow sex: It sounds as if you were doing this as a discipline.
And, if I may say so: as your discipline. (With a stress on you, and not on your wife.)
How was this for your wife? Was she also in to Goenka-style meditation when you both started on this way of improving the relationship?
You did eight years of Goenka-style vipassana. And then you combined that with tantra (slow sex) for two years. As far as I know Goenka forbids to do other spiritual practices, and Goenka regards sexual longing and sexual activity as something to overcome. Correct me if I am wrong, but it sounds as if you decided to combine the way of Goenka with something that he does not want his students to be combine things.
In my view, the body scanning techinque is so basic that it can easily be combined with a lot of spiritual disciplines. I learned body scanning as a part of Natural Dance, from a pupil of Anna Halprin. But that scanning does not have the theoretical and spiritual setting and meaning that it has with Goenka.
Again: Correct me if I am wrong, but to me it sounds as if for two years you did something of which you knew that Goenka would regard it as wrong. Without taking leave from Goenka at the start of you tantra-exercises.
So in this perspective - and it might just be my fantasy - you have a headache form a fight between two different spiritual disciplines. At least, one discipline fights the other. In this perspective, being in a battle zone drains your energy.
(I knew a few ladies here in Holland, who longed for sex, but felt that sex was bad, due to their religious conviction. They had a feeling of guilt by default. They suffered from guilt. And they decided to change their religion to a milder form. A whole generation did that. Sex is no longer regarded as something filthy by the Christians of today here in Holland.
That would be comparable, if this perspective were right.)
So, that is three perspectives.
I hope that this helps.
How is your wife?
P.S.: If meditation is that bad for you, I do not see why you should be sorry not to do it any more.