I have headache from few months in half head on left side. 24 yr old female?

Localized headache. Headaches located on one side can be migraines, cluster headaches or things more ominous. I would suggest starting a headache diary and making an appt to see your doc right away to figure this headache out and get it under control. You need to figure out what kind of headache it is and then treat the cause. http://www.headaches.org/for_professionals/headache_diary.
Tension headache. The most likely diagnosis is chronic daily headache related to your total life situation, however even in a young person other causes have to be ruled out. Are you taking the contraceptive pill or other meds, sleep pattern? Blood pressure? See your neurologist.