Hi, I had earlier asked few questions above so that I can gather additional information related to your health concerns about the severe headache you are recently suffering from. It is possible you are encountering some technical glitches to access this site properly or you may be busy now and not in a position to reply, so what I will do is post an initial answer here based on the amount of information I have received through your initial question here, please go through it when your time permits & when you can, and please get back to me if you want to discuss this further.
Please see headache is a very common symptom and the good news is majority of the headaches are not at all due to any underlying serious conditions, so despite the fact that it is very severe and new onset this still most likely is not related to any underlying serious conditions, and I am reassuring you in this regard. Also as I had mentioned earlier stopping warfarin is not expected to cause this kind of headache.
Migraine headaches can present like this severely (if you have history of migraines also if you are having other classical symptoms of migraine like sensitivity to light or sound, pulsatile type headache, nausea or vomiting etc – if you are not having these additional symptoms then this is unlikely from migraine)
Conditions like meningitis can do this but if you are not having any fever or nausea or vomiting etc then meningitis is unlikely
Bleeding in the brain can cause severe headache but this possibility is actually more if someone is on blood thinner like warfarin but you have now come off it so if at all the risk of bleeding is minimized in you due to stopping the blood thinner so bleeding also does not appear to be the possibility to explain this headache
High blood pressure too can cause severe headaches like this, so if you have not checked the blood pressure after this headache started then you may get it checked now asap because if this is related to high blood pressure then the blood pressure needs to be normalized quickly
Tension headaches can present very severe like this, I am not sure whether you are under any obvious stress now, even if you are not under any obvious stress but considering the fact that an important medication (warfarin) being stopped so you may be worrying what can happen in the absence of the blood thinner, and also a surgery is coming soon - so there may be some unrecognized stress and that may manifest with severe headache like this. I am not telling this is indeed the reason for this headache, I am just mentioning the possibilities.
Since the headache is very severe and persisting and this type of headache is new to you so this needs to be evaluated and investigated further. You may try to visit the nearest er so that you can receive a thorough neurological examination including blood pressure measurement (if not done already) followed by a brain scan like CAT scan of the brain and this will serve as workup for this severe headache. However with experience I am writing this - irrespective of the severity of the headaches the majority of these types of severe headaches are not due to any serious conditions so please not to be scared. You may try to get this evaluated and investigated this in the er with cat scan of the brain as mentioned above but like I said earlier this is most likely not secondary to any serious underlying conditions and I reassure you in this regard and the visit to the er and the brain scan etc are mainly as a precautionary measure – just to be on the safer side.
Please go through the above answer which is based on what information I had gathered from your original question. If you want to discuss this further or if you need any additional clarifications please get back to me, and also please try to provide me the additional information I had inquired earlier through the questions I had posted above and I am available here for further discussions until you are satisfied. And please click a positive rating (preferably 5 Star/Excellent) to credit for the time & effort put by me in answering your health question, and this is the only way I will be credited for my service to you. If you have follow-up or additional questions you can ask them after the rating too.