<s>[INST] I am having occasional pain during sex at the base of my head where it meets the spine. It only happens occasionally and only after orgasm. It feels like a knife was shoved in the back of my neck. The pain lasts about 10 to 15 minutes..... It is really intense pain. [/INST] Hello and thanks for using Chat Doctor. I have read your question and understand your concerns. Sex headaches in most cases are nothing to worry about, but in rare cases, they may be associated with underlying conditions such subarachnoidal hemorrhage, dissection of arteries, arteriovenous malformations, etc. especially if they happen suddenly. So, before to be sure that there is nothing wrong with these headaches, getting evaluated by a Neurologist and by imaging studies (MRI) is necessary. Hope you found the answer helpful. Kind regards. </s>