Whenever i stretch, my back hurts. it hurts so much! what can it depend on?

For a young person: Like you it is very unusual to have such symptoms just from stretching alone . Do you have any pain when you bend , walk , getting up from lying or sitting position ? Do you have any tenderness in the back bone or on the side if the hip bones . If the condition continue and is not going away , it is always better to see your doc. Good luck.