If you're wondering why you get bad headaches before or at the start of orgasm that last anywhere from 10 minutes to a few hours, it is caused by the muscle tension that leads to climaxing. Pain is felt around or behind the eyes. These sex-related headaches are becoming norm it seems. If you get these headaches, it would be best to consult your doc so the trigger can be determined and he can prescribe proper treatment. I have also read that it could be a sign of high blood pressure because at the time of orgasm, blood pressure rises slightly.