Pop in the head while vomitting followed by the worst headache ever typically describes Subarachnoid haemorrhage(SAH) which is bleeding between the fibrous layers surrounding the brain and it will be accompanied other symptoms like confusion, diminished consciousness, stiff neck
, seizures, etc. depending upon the severity of bleed... It may be present as severe head ache alone in minor bleeds. It needs immediate evaluation with head CT, if needed lumbar puncture
Appearance of similar headache on sneezing
is also favourable of SAH but if it comes again it will be more severe and worst and the outcome will also be worse. The fact that it is weaning off goes against SAH and it points towards tension headache
However it should not be ignored as SAH is extremely dangerous and it needs to be ruled out as the chances of rebleed is also high. Meanwhile take complete rest and avoid straining in any form till this is sorted out..