Hello dr.have got some kind of pain at the end of my back actually within the waist.when i sit for long or try to bend it just appears any advise...

Muscle spasm: If is new rest the back from vigorous lifting, pushing, or pulling. Use an heating pad. If problem persists you might need an examination and perhaps an mri. Absent some significant back injury in your medical history, your young age does not support a degenerated disk. Were you an extreme sports enthusiast? If so you might have fallen on your buttocks too many times and incurred your pelvis.