I have severe lower back pain. i am only a teen and i am active not lazy. it hurts when i sit or stand for a long time. it feels like my tailbone.

Nonspecific: Your complaint is fairly nonspecific and a number of conditions could be the cause, such as early degenerative disc, herniated disc, pinched nerve, facet mediated pain, coccydynia, intra-pelvic pathology, etc. A medical evaluation would certainly be advised if pain has been persistent and/or severe.

Back pain in young: Young patients rarely need further evaluation for back pain as it is usually self-limiting. For mild symptoms, muscle pains are most common. Consider also disc herniation which may cause pain without sciatica. Stress fracture (spondylolysis) occurs in 5% of the population without any symptoms. If symptoms persist, then see your doc for a more specific evaluation.