I have lower back pain from last 6 years . ir some time completely disapear and sometime become very severe, physical theraphy or exercise please ?

Both are helpful: P.T and exercise can be helpful and in fact the best type of p.T. For back problems is an exercise based program. Hands on, passive therapy is not likely to help much so an active, exercise program is best. If you smoke cigarettes, stop smoking. Good research shows that smokers have more pain.

Exercise: Routine low impact aerobic exercise can reduce your overall pain (i.e. Walking cycling swimming) i would check with your primary doctor as well. Physical therapy may prescribed.