Is it a tear? Is it a Strain? Is it a Pull?

Exactly 2 months and 2 days ago (2-14-11) I hurt my back lifting weights, doing power cleans. I'm 13 years old 5'5 135 pounds. Very active. I stayed off of it for about 2 weeks cause I didn't know what was going on. it just hurt when I would turn or something. After the 2 weeks I just returned to being very active. Doing activities hurt some but I just kept playing. I didn't lift weights. I skateboarded and constantly rode bikes. I did sprints in Athletics for school 2 days ago and my back has hurt since then, I just sucked it up and kept playing. It hurts when i twist, bend over, jump and land on something not steady, squat, sprint, thing like that. What's going on? :(