Why  do I have this strong headaches when I stand up?

Must find out why. New onset of headaches, no matter what the characteristics, or change in the pattern of ha that have become chronic, or persistent/recurrent headaches that have never been evaluated by a primary care soc or neurologist, must be worked up. Suggest finding a good internist and have a thorough check-up.
Neurology consult. That is a strange presentation of a headache and could very likely mean a neurological problem. Consult a neurologist.