Left side brain is painning ,little loose motion iam a chain smoker,is that a reason ?

See your physician: There are many types of headaches and many reasons for each type. You should see your primary care physician first. It would be helpful for you to keep a "headache calendar" by noting down the frequency, duration, location, and intensity of your headaches, along with associated symptoms. Also note your headache "triggers," which may include smoking. http://www.nlm.nih.gov/medlineplus/headache.html