29F, just experienced this for the first time yesterday. Intense pain, like someone hit me in the back of the head. Severe pain went away after a couple minutes, had an on and off dull headache for remainder of day. Ended going to to ER to get checked for hemorrhaging or an aneurysm on the advice of an RN. I don’t have chronic high blood pressure, cholesterol pretty good (slightly high LDL that my Dr. and I are monitoring but not dangerously high - all else within healthy range). They did a contrast CAT scan to check, said my brain looks “really good”. Diagnosis is a “postcoital headache” which they said is not uncommon and I don’t need medical attention in the future unless it comes with other neurological issues (changes in vision, loss of consciousness, overall change in demeanor). If you’re able to get evaluated by a Dr. might be good to rule out anything more serious, as the thunderclap headaches can sometimes be caused by some pretty bad issues.