Hello,I have gone through your problem. You did not mention your age,sex,past history of any disease or intake of medication. However,from your presenting complaints,I would suggest you to do following things as soon as possible:
(1) Get Checked your Blood Pressure,pulse rate-(in view of any heart rhythm abnormailties or Hypotension
(2)Get an ECG done (to check any abnormalities of conduction pathways of heart)
(3)Do a CT scan
of Brain (as you mentioned that you are having big headache & feeling drowsy. There may be a possibility of "Sub Dural Hemorrhage" i.e. accumulation of blood under dural layer of brain).
(4)Check your hydration status and urine output (in view of possible dehydration
Hope,this will help. Thank you.
Dr. Sudipto Modak