Hello! Thank you for asking on HCM! Regarding yuor concern, i think that you problems may be related to orthostatic hypotension or orthostatic headache, although it is not very typical of this disorder to feel back the pain, when sitting back. Another cause would be sleep deprivation. I recommend monitoring your blood pressure during sitting and standing up position. A decrease in your systolic blood pressure more than 20mm Hg, would be indicative or orthostatic hypotension. A head up tilt test would be necessary to exclude the possible cause. I also advise consulting a neurologist for a careful physical examination. A brain CT scan may be needed if suspicions are raised during physical examination. Hope to have been of help! Best wishes! Dr. Aida