If I lift heavy my back starts paining for atleast a week it continues. M 17 yrs 66kg 5 feet 5inches before a year. There ws no problem of back pain.

Musculoskeletal pain. You are too young to cause any significant back pain Proper lifting techniques are important . Local heat like hot shower. Back strengthening exercises.
Get it checked out. If your back is hurting when you lift, something is going on. It may be as simple as your mechanics when you lift, but it can also be something more. At this point, since it has been going on for some time, I do recommend you be evaluated by a spine specialist to make sure you don't have an injury. .
Lumbar strain. Localized lower back pain can be related in young person to disc rupture especially if there is previous history of significant back injury. Statistically without seeing X-rays and with limited history it can be considered to represent lumbar strain. More information regarding type of the pain, and past history of injury would be very helpful to making more precise diagnosis of this condition.