Why i have a strong headache during sleep and then when i wake up and get out of bed it goes away?

Headaches: You have what are called hypnic headaches or alarm clock headaches.This form of headache is a rare type of headache which usually affect older people. However, younger people may be affected. The headache may be a dorm of migraines. Drugs like indocin (indomethacin) or melatonin seem to help. However, as a caveat I would recommend you see a neurologist or a sleep expert