I have had headach in half head on left side including neck please tell me the reason or is it because of tension ? i asked befor too. thank you

Likely primary : Most headaches not serious. However, first your doctor will determine what type of headache you have. Headaches have many causes i suggest you see your physician and discuss a plan to determine the cause. Your doctor might order imaging of brain and optic nerve exam to rule out serious conditions. Hope it helps.

Tension: It is likely a tension headache but you should see a doctor to have your neck examined to be sure you don't have a herniated disc.