HI Well come to HCM First of all this is not headache nor this is a disease but this is just a condition, erection actually takes places with the helps of sexual stimulation, and these are, visual, talk, touch, thinking, about the sex and this is all happens in the cortex area of brain, even slight mental condition could disturb this process, and most of the time emotional stress would be the cause behind this, low down your stress level, stop guilty feeling for masturbation, every would be fine, take care.