I am feeling headache in back side of head from last 4 months. it occurs just above neck and side of back head ..like some nerve is blocked. it feels like needle type. after exercise it gets cured. but after sometime it again starts . after sleeping also it gets cured . but again after waking up it starts ..sometime i feels like brain fog . means cant see clearly due to this.. my eyesight is ok . bp in range 130/80 to 140/85 . 2 months ago my headache was just after eating something even after drinking tea it starts immediately and it was in whole head. but now it occurs in back head above neck . and anytime of day... what should i do please help. lifestyle ok